Electro-optical liquid crystal display element

ABSTRACT

The invention relates to an electro-optical liquid crystal display element containing a dielectric with at least two liquid-crystalline components, wherein the dielectric, for shortening the switching times, contains at least one fluorine-containing compound of the formula I 
     
         R.sup.1 --(A.sup.1 --Z.sup.1).sub.m --A.sup.2 --R.sup.2    I 
    
     wherein the radicals R 1 , R 2 , A 1 , A 2 , Z 1  and m have the meaning given in claim 1.

This is a division, of application Ser. No. 07/294,630 filed Dec. 23,1988, U.S. Pat. No. 5,196,140.

The invention relates to an electro-optical liquid crystal displayelement containing a dielectric with at least two liquid-crystallinecomponents, characterized in that, for shortening the switching times,the dielectric contains at least one fluorine-containing compound of theformula I

    R.sup.1 --(A.sup.1 --Z.sup.1).sub.m --A.sup.2 --R.sup.2    I

wherein

one of the radicals R¹ and R² is H, F, Cl, Br, --CN, --NCS or anunsubstituted or substituted alkyl group having 1-15 C atoms, in whichone or two CH₂ groups can also be replaced by a grouping selected fromthe group comprising --O--, --CO--, --O--CO--, --CO--O--,--CH--halogen--, --CHCN--, --CCH₃ CN--, --C.tbd.C-- and --CH═CH--, no 2heteroatoms being directly linked to one another,

the other radical R¹ or R² is a perfluoroalkyl group having 1-15 Catoms, in which one or more CF₂ groups can also be replaced by agrouping selected from the group comprising --O--, --CO--, --O--CO--,--CO--O--, --CH₂ --, --CH--halogen--, --CHCN--, --C.tbd.C--, --CH═CH--,--CH═C--halogen-- and --C--halogen═C--halogen--, no two heteroatomsbeing directly linked to one another and the perfluoroalkyl groupcontaining at least two CF₂ groups,

A¹ and A² independently of one another are each 1,4-phenylene which isunsubstituted or substituted by one or two F and/or CL atoms and/or CH₃groups and/or CN groups and in which one or two CH groups can also bereplaced by N atoms, 1,4-cyclohexylene in which one or two non-adjacentCH₂ groups can also be replaced by O atoms and/or S atoms,piperidine-1,4-diyl, 1,4-bicyclo[2.2.2]octylene, unsubstituted orCN-substituted decahydronaphthalene-2,6-diyl or1,2,3,4-tetrahydronaphthalene-2,6-diyl, and A² is also a single bond,

m is 0, 1, 2 or 3 and

Z¹ is --CO--O--, --O--CO--, --OCH₂ --, --CH₂ O--, --CH₂ --CH₂ --,substituted ethylene or a single bond,

it being possible for the groups A¹ and Z¹ to be identical or differentin the case of m=2 or 3, with the proviso that, in the case of m=0, thesum of the number of C atoms in the two groups R¹ and R² is at least 8,and to fluorine-containing additives for liquid-crystalline dielectricswhich are suitable for shortening the switching times in electro-opticalliquid crystal display elements. The invention also relates to novelcompounds of the formula I, which correspond to the formulae I, III andIV.

Liquid-crystalline dielectrics can be used in various electro-opticaldisplay elements, in particular in displays which . . . (sic) on theprinciple of the twisted cell (TN displays), the Guest-Host effect, theeffect of the deformation of aligned phase, the effect of dynamicscattering, the SBE effect (supertwisted birefringent effect), in STNdisplays (supertwisted nematic displays) and in ferroelectric displays,for example based on SSFLC technology. The expression "dielectric" usedin this application thus relates to mixtures which contain a nematic,cholesteric or smectic (especially Sc*) mesophase.

In order to be suitable for the display elements listed above, thedielectrics must meet a large number of very diverse demands matched tothe particular display principle, which, however, include in virtuallyevery case very short switching times which, inter alia, can also beachieved by viscosity-reducing additives. Such additives have alreadybeen described in the literature (German Offenlegungsschrift 2,548,360,German Offenlegungsschrift 2,823,909). Disadvantages of these knownadditives are, however, the lowering of the clear point which must beaccepted and/or the high vapor pressure of these additives.

It was the object of the invention to provide novel stable dielectricswith fluorine-containing additives, which do not show the abovedisadvantages, or only to a small extent.

It has now been found that the compounds of the formula I areoutstandingly suitable as additives for diverse dielectrics.

Moreover, by the provision of the compounds of the formula I, the rangeof additives for liquid-crystalline dielectrics, which are suitable forthe preparation of liquid-crystalline mixtures under various applicationaspects, is quite generally widened considerably.

For the sake of simplicity, in the text which follows, Phe designates a1,4-phenylene group, Cy designates a 1,4-cyclohexylene group, Diodesignates a 1,3-dioxane-2,5-diyl group, Bi designates abicyclo(2,2,2)octylene group, Pyd designates a pyridine-2,5-diyl groupand Pyr designates a pyrimidine-2,5-diyl group, it being possible forthese groups to be unsubstituted or substituted.

The compounds of the formula I have a wide range of application.Depending on the choice of the substituents, these compounds can beadded to liquid-crystalline dielectrics, which are suitable for the mostdiverse applications, from other classes of compounds.

The invention thus relates to electro-optical liquid crystal displayelements containing a dielectric with at least two liquid-crystallinecomponents, characterized in that, for shortening the switching times,the dielectric contains at least one fluorine-containing compound of theformula I

    R.sup.1 --(A.sup.1 --Z.sup.1).sub.m --A.sup.2 --R.sup.2    I

wherein

one of the radicals R¹ and R² is H, F, Cl, Br, --CN, --NCS or anunsubstituted or substituted alkyl group having 1-15 C atoms, in whichone or two CH₂ groups can also be replaced by a grouping selected fromthe group comprising --O--, --CO--, --O--CO--, --CO--O--,--CH--halogen--, --CHCN--, --CCH₃ CN--, --C.tbd.C-- and --CH═CH--, no 2heteroatoms being directly Linked to one another,

the other radical R¹ or R² is a perfluoroalkyl group having 1-15 Catoms, in which one or more CF₂ groups can also be replaced by agrouping selected from the group comprising --O--, --CO--, --O--CO--,--CO--O--, --CH₂ --, --CH--halogen--, --CHCN--, --C.tbd.C--, --CH═CH--,--CH═C--halogen-- and --C--halogen═C--halogen--, no two heteroatomsbeing directly Linked to one another and the perfluoroalkyl groupcontaining at Least two CF₂ groups,

A¹ and A² independently of one another are each 1,4-phenylene which isunsubstituted or substituted by one or two F and/or Cl atoms and/or CH₃groups and/or CN groups and in which one or two CH groups can also bereplaced by N atoms, 1,4-cyclohexylene in which one or two non-adjacentCH₂ groups can also be replaced by O atoms and/or S atoms,piperidine-1,4-diyl, 1,4-bicyclo[2.2.2]octylene, unsubstituted orCN-substituted decahydronaphthalene-2,6-diyl or1,2,3,4-tetrahydronaphthalene-2,6-diyl, and A³ is also a single bond,

m is 0, 1, 2 or 3 and

Z¹ is --CO--O--, --O--CO--, --OCH₂ --, --CH₂ O--, --CH₂ --CH₂ --,substituted ethylene or a single bond,

it being possible for the groups A¹ and Z¹ to be identical or differentin the case of m=2 or 3, with the proviso that, in the case of m=0, thesum of the number of C atoms in the two groups R¹ and R² is at least 8,and to liquid-crystalline dielectrics with at least twoliquid-crystalline components which contain at least one compound of theformula I.

The invention also relates to the use of the compounds of the formula Ias components of liquid-crystalline dielectrics for electro-opticaldisplay elements, to fluorine compounds of the formula II

    R.sup.1 --(A.sup.1 --Z.sup.1).sub.m --A.sup.2 --R.sup.2    II

wherein

one of the radicals R¹ and R² is H, F, Cl, Br, --CN, --NCS or anunsubstituted or substituted alkyl group having 1-15 C atoms, in whichone or two CH₂ groups can also be replaced by a grouping selected fromthe group comprising --O--, --CO--, --O--CO--, --CO--O--,--CH--halogen--, --CHCN--, --CCH₃ CN--, --C.tbd.C-- and --CH═CH--, no 2heteroatoms being linked directly to one another,

the other radical R¹ or R² is a perfluoroalkyl group having 1-15 Catoms, in which one or more CF₂ groups can also be replaced by agrouping selected from the group comprising --O--, --CO--, --O--CO--,--CO--O--, --CH₂ --, --CH--halogen--, --CHCN--, --C.tbd.C--, --CH═CH--,--CH═C--halogen-- and --C--halogen═C--halogen--, no two heteroatomsbeing linked directly to one another and the perfluroalkyl groupcontaining at least two CF₂ groups,

A¹ is trans-1,4-cyclohexylene which is unsubstituted or substituted byone or two F and/or Cl atoms and/or CH₃ groups and/or CN groups and inwhich one or two non-adjacent CH₂ groups can also be replaced by Oand/or S or --CH-- groups can be replaced by N,1,4-bicyclo[2.2.2]octylene, decahydronaphthalene-2,6-diyl or1,2,3,4-tetrahydronaphthalene-2,6-diyl,

A² is 1,4-phenylene which is unsubstituted or substituted by one or twoF and/or Cl atoms and/or CH₃ groups and/or CN groups and in which one ortwo CH groups can also be replaced by N atoms, 1,4-cyclohexylene inwhich one or two non-adjacent CH₂ groups can also be replaced by O atomsand/or S atoms, piperidine-1,4-diyl, 1,4-bicyclo[2.2.2]octylene,unsubstituted or CN-substituted decahydronaphthalene-2,6-diyl or1,2,3,4-tetrahydronaphthalene-2,6-diyl,

m is 0 or 1 and

Z¹ is --CO--O--, --O--CO--, --OCH₂ --, --CH₂ O--, --CH₂ --CH₂ --,substituted ethylene or a single bond, and to nitrogen-containingheterocyclic compounds of the formula III

    R.sup.1 --A.sup.1 --(Z.sup.1 --A.sup.2).sub.P --R.sup.2    III

wherein

one of the radicals R¹ and R² is H, F, Cl, Br, --CN, --NCS or anunsubstituted or substituted alkyl group having 1-15 C atoms, in whichone or two CH₂ groups can also be replaced by a grouping selected fromthe group comprising --O--, --CO--, --O--CO--, --CO--O--,--CH--halogen--, --CHCN--,--C.tbd.C-- and --CH═CH--, no 2 heretoatomsbeing directly linked to one another,

the other radical R¹ or R² is a perfluoroalkyl group having 1-15 Catoms, in which one or more CF₂ groups can also be replaced by agrouping selected from the group comprising --O--, --CO--, --O--CO--,--CO--O--, --CH₂ --, --CH--halogen--, --CHCN--, --C.tbd.C--, --CH═CH--,--CH═C--halogen-- and --C--halogen═C--halogen--, no two heteroatomsbeing directly linked to one another and the perfluoroalkyl groupcontaining at least two CF₂ groups,

A¹ is A³ --Z² --Z-- or --A--Z² --A³ --,

A is a 1,4-phenylene group in which at least one CH group is replaced byN,

A³ is 1,4-phenylene which is unsubstituted or substituted by one or twoF and/or Cl atoms and/or CH₃ groups and/or CN groups and in which one ortwo CH groups can also be replaced by N atoms,

A² is 1,4-phenylene which is unsubstituted or substituted by one o r twoF and/or Cl atoms and/or CH₃ groups and/or CN groups and in which one ortwo CH groups can also be replaced by N atoms, 1,4-cyclohexylene inwhich one or two non-adjacent CH₂ groups can also be replaced by O atomsand/or S atoms, piperidine-1,4-diyl, 1,4-bicyclo[2.2.2]octylene,unsubstituted or CN-substituted decahydronaphthalene-2,6-diyl or1,2,3,4-tetrahydronaphthalene-2,6-diyl,

Z¹ and Z² independently of one another are each --CO--O--, --O--CO--,--OCH₂ --, --OCH₂ O--, --CH₂ CH₂ --, substituted ethylene or a singlebond and

p is 0, 1 or 2,

it being possible for the groups Z¹ and A² to be identical or differentin the case of p=2.

The invention also relates to fluorine compounds of the formula IV

    R.sup.1 --(A.sup.1 --Z.sup.2).sub.m --A.sup.2 --R.sup.2    IV

wherein

R¹ is an alkyl group having 1-15 C atoms, in which one or two CH₂ groupscan also be replaced by a grouping selected from the group comprising--O--, --CO--, --O--CO--, --CO--O--, --CH--halogen--, --CHCN--, --CCH₃CN--, --C.tbd.C-- and --CH═CH--, no 2 heteroatoms being directly linkedto one another,

R² is a perfluoroalkyl group having 1-15 C atoms, in which one or moreCF₂ groups can also be replaced by a grouping selected from the groupcomprising --O--, --CO--, --O--CO--, --CO--O--, --CH₂ --,--CH--halogen--, --CHCN--, --C.tbd.C--, --CH═CH--, --CH═C--halogen-- and--C--halogen═C--halogen--, no two heteroatoms atoms being directlylinked to one another and the perfluoroalkyl group containing at leasttwo CF₂ groups,

A¹ is 1,4-cyclohexylene in which one or two nonadjacent CH₂ groups canalso be replaced by O atoms and/or S atoms,

A² is 1,4-phenylene which is unsubstituted or substituted by one or twoF atoms,

m is 1 or 2 and

Z¹ is --CO--O--, --O--CO--, --OCH₂ --, --OCH₂ O--, --CH₂ --CH₂ -- or asingle bond,

it being possible for the groups A¹ and Z¹ to be identical or differentin the case of m=2. In the case of m=1, A² is here preferably 1,4-phenylene which is substituted by one or two F atoms.

In the preceding and following text, R¹, R², A¹, A², A³, A, Z¹, Z², mand p have the meaning given under the formulae I, II, III and IV,unless specifically stated otherwise.

The compounds of the formula I accordingly comprise in particularcompounds of the part formulae Ia, Ib (with 1 ring), Ic (with 2 rings),Id (with 3 rings) and Ie (with 4 rings):

    R.sup.1 --R.sup.2                                          Ia

    R.sup.1 --A.sup.2 --R.sup.2                                Ib

    R.sup.1 --A.sup.1 --Z.sup.1 --A.sup.2 --R.sup.2            Ic

    R.sup.1 --A.sup.1 --Z.sup.1 --A.sup.1 --Z.sup.1 --A.sup.2 --R.sup.2Id

    R.sup.1 --A.sup.1 --Z.sup.1 --A.sup.1 --Z.sup.1 --A.sup.1 --Z.sup.1 --A.sup.2 --R.sup.2                                       Ie

Compounds of the formulae Ic are particularly preferred. In thecompounds of the formulae Id and Ie, the groups A¹ and Z¹ can beidentical or different. The groups Z¹ are here preferably single bonds.Those compounds of the formulae Id or Ie are also preferred which one ofthe groups Z¹ is --CH₂ CH₂ --, --O--CO-- or --CO--O-- and the othergroup(s) Z¹ is or are a single bond.

The compounds of the formula Ia comprise those of the preferred partformulae Iaa-Iae:

    C.sub.n F.sub.2n+1 --C.sub.m H.sub.2m+1                    Iaa

    C.sub.n F.sub.2n+1 OCF.sub.2 CF.sub.2 OC.sub.m H.sub.2m+1  Iab

    C.sub.n F.sub.2n+1 OCF.sub.2 CF.sub.2 OCF.sub.2 CF.sub.2 OC.sub.m H.sub.2m+1Iac

    C.sub.n F.sub.n+1 COCH.sub.2 COC.sub.m H.sub.2m+1          Iad

    C.sub.n F.sub.n+1 CN                                       Iae

Those of the part formula Iaa are particularly preferred amongst these.

The compounds of the formula Ib comprise those of the preferred partformulae Iba-Ibd:

    C.sub.n F.sub.2n+1 CyCN                                    Iba

    C.sub.n F.sub.2n+1 CyC.sub.m H.sub.2n+1                    Ibb

    C.sub.n F.sub.2n+1 CyOC.sub.m H.sub.2m+1                   Ibc

    C.sub.n F.sub.2n+1 PheCN                                   Ibd

Those of the part formula Iba are particularly preferred amongst these.

In these part formulae Iaa to Ibd, n and m are each independently of oneanother 1-5, preferably 2-8.

The compounds of the formula Ic comprise those of the preferred partformulae Ica to Icd:

    R.sup.1 --Cy--Z.sup.1 --Cy--R.sup.2                        Ica

    R.sup.1 --Cy--Z.sup.1 --Phe--R.sup.2                       Icb

    R.sup.1 --Phe--Z.sup.1 --Phe--R.sup.2                      Icc

    R.sup.1 --Phe--Z.sup.1 --Pyr--R.sup.2                      Icd

Those of the part formula Icb are particularly preferred amongst these.

The compounds of the formula Id comprise those of the preferred partformulae Ida to Idg:

    R.sup.1 --Phe--Z.sup.1 --Phe--Z.sup.1 --Cy--R.sup.2        Ida

    R.sup.1 --Pyr--Z.sup.1 --Phe--Z.sup.1 --Cy--R.sup.2        Idb

    R.sup.1 --Phe--Z.sup.1 --Pyr--Z.sup.1 --Cy--R.sup.2        Idc

    R.sup.1 --Cy--Z.sup.1 --Phe--Z.sup.1 --Phe--R.sup.2        Idd

    R.sup.1 --Cy--Z.sup.1 --Cy--Z.sup.1 --Phe--R.sup.2         Ide

    R.sup.1 --Cy--Z.sup.1 --Phe--Z.sup.1 --Cy--R.sup.2         Idf

    R.sup.1 --Cy--Z.sup.1 --Cy--Z.sup.1 --Cy--R.sup.2          Idg

One of the radicals R¹ and R² is preferably alkyl, alkoxy, alkanoyloxy,alkoxycarbonyl, oxaalkoxy or oxaalkyl having preferably 2 to 12 C atoms.Alkyl is particularly preferred.

A¹ and A² are preferably Cy, Phe or Pyr. Preferably, the compounds ofthe formula contain only one Pyr or Dio group. m is preferably 1 or 2and especially preferably 1.

The alkyl radicals in the groups R¹ and/or R² can be straight-chain orbranched. Preferably, they are straight-chain, have 2, 3, 4, 5, 6, 7, 8,9, 10, 11 or 12 C atoms and, accordingly, preferably are ethyl, propyl,butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl or dodecyl,and also methyl, tridecyl, tetradecyl or pentadecyl.

If these radicals are alkyl radicals in which one ("alkoxy" or"oxaalkyl") or two ("alkoxyalkoxy" or "dioxaalkyl" CH₂ groups arereplaced by O atoms, these can be straight-chain or branched.Preferably, they are straight-chain, have 2, 3, 4, 5, 6 or 7 C atomsand, accordingly, are preferably ethoxy, propoxy, butoxy, pentoxy,hexoxy, heptoxy, 2-oxapropyl (=methoxymethyl), 2-(=ethoxymethyl) or3-oxabutyl (=2-methoxyethyl), 2-, 3- or 4-oxapentyl, 2-, 3-, 4- or5-oxahexyl, 2-, 3-, 4-, 5- or 6-oxaheptyl, and also methoxy, octoxy,nonoxy, decyloxy, 2-, 3-, 4-, 5-, 6- or 7-oxaoctyl, 2-, 3-, 4-, 5-, 6-,7- or 8-oxanonyl, 2-, 3-, 4-, 5-, 6-, 7-, 8- or 9-oxadecyl,1,3-dioxabutyl (=methoxymethoxy), 1,3-, 1,4- or 2,4-dioxapentyl, 1,3-,1,4-, 1,5-, 2,4-, 2,5- or 3,5-dioxahexyl or 1,3-, 1,4-, 1,5-, 1,6-,2,4-, 2,5-, 2,6-, 3,5-, 3,6- or 4,6-dioxaheptyl.

Compounds of the formula I and of the part formulae given above andbelow with branched wing groups can sometimes be of importance becauseof higher solubility in the usual liquid-crystalline base materials, butespecially as chiral doping agents, if they are optically active. Suchcompounds are also suitable as components of ferroelectric materials.Branched groups of this type do not as a rule contain more than onechain branching. Preferred branched radicals are isopropyl, 2-butyl(=1-methylpropyl), isobutyl (=2-methylpropyl), 2-methylbutyl, isopentyl(=3-methylbutyl), 2-methylpentyl, 3-methylpentyl, 2-ethylhexyl,2-propylpentyl, 2-octyl, isopropoxy, 2-methylpropoxy, 2-methylbutoxy,3-methylbutoxy, 2-methylpentoxy, 3-methylpentoxy, 2-ethylhexoxy,1-methylhexoxy, 1-methylheptoxy, 2-oxa-3-methylbutyl,3-oxa-4-methylpentyl and 2-octyloxy.

One of the two radicals R¹ and R² in the compounds of the formulae I, IIand III and R² in the compounds of the formula IV is a perfluoroalkylgroup having 1-15 C atoms, in which one or more CF₂ groups can also bereplaced by a grouping selected from the group comprising --O--, --CO--,--O--CO--, --CO--O--, --CH₂ --, CHhalogen, --CHCN--, --C.tbd.C--,--CH═CH--, --CH═CHhalogen-- and Chatogen═C--halogen--, no twoheteroatoms being directly linked to one another and the perfluoroalkylgroup containing at least two CF² groups. The perfluoroalkyl groupdefined accordingly is preferably of the formula

    --X'--Q'--Y'--R.sup.5

in which

X' is ---O--O--, --O--CO--, --O--CO--O--, --CO--, --O--, --S--,--CH═CH--, --CH═CH--COO--, --CH₂ CH₂ --, --CH₂ CH₂ -- COO-- or a singlebond,

Q' is alkylene having 1 to 5 C atoms, in which one CH₂ group not linkedto X' can also be replaced by --O--, --CO--, --O--CO--, --CO--O-- or--CH═CH--, or a single bond,

Y' is perfluoroalkylene having 2 to 15 C atoms, in which one or more CF₂groups can also be replaced by --CHF-- or --CF═CF--, and

R⁵ is H, F or an alkyl group having 1 to 5 C atoms, in which one or twonon-adjacent CH₂ groups can also be replaced by --O--, --CO--,--O--CO--, --CO--O-- and/or --CH═CH--,

with the proviso that the group of the formula --X'--Q'--Y'--R⁵ does notcontain more than 15 C atoms in total and contains at least two CF₂groups.

X' is preferably --O--, --O--CO--, --CO--O--, --CH═CH--(trans), --CH₂CH₂ --, --COO--CH₂ -- or a single bond.

Q' is preferably --CH₂ -- or a single bond. Y' is preferablystraight-chain perfluoroalkylene having 2 to 8 C atoms, especiallypreferably 2 to 6 C atoms. R⁵ is preferably H or F, especiallypreferably F.

Particularly preferred radicals --X'--Q'--Y'--R⁵ are thus R_(F),--O--R_(F), --CH═CH--R_(F), --CH₂ CH₂ --R_(F) --COO--R_(F), --OOCR_(F),--COO--CH₂ --R_(F) and --OOC--CH₂ --R_(F), wherein R_(F) is a preferablystraight-chain perfluoroalkyl group in which one F (especially in theω-position) can also be replaced by H.

Very particularly preferred radicals --X'--Q'--Y'--R⁵ are, for example,those of the formulae 1-13:

    --OC.sub.2 F.sub.5                                         1

    --C.sub.2 F.sub.5                                          2

    --OC.sub.2 F.sub.4 H                                       3

    --C.sub.3 F.sub.7                                          4

    --CO--C.sub.8 F.sub.17                                     5

    --COO--CH.sub.2 --CF.sub.2 --CHF.sub.2                     6

    --CH═CH--C.sub.6 F.sub.13                              7

    --CH.sub.2 CH.sub.2 --C.sub.6 F.sub.13                     8

    --CH.sub.2 CH.sub.2 --C.sub.3 F.sub.7                      9

     CH═CH--COO--CH.sub.2 CH.sub.2 --C.sub.8 F.sub.17      10

    --CH═CH--COO--CH.sub.2 --C.sub.4 F.sub.8 H             11

    --C.sub.6 F.sub.13                                         12

    --C.sub.9 F.sub.19                                         13

A¹ and A² are preferably Cy, Phe or Pyr, and Phe can, if appropriate,also be 1,4-phenylene laterally substituted by fluorine. Z¹ and Z² arepreferably --CO--O--, --O--CO--, --CH₂ CH₂ -- or single bonds,especially preferably single bonds. m is preferably 1.

Some of the compounds of the formula I are novel (especially those ofthe formula II, III and IV). All the compounds of the formula I areprepared by methods known per se, such as are described in theliterature (for example in the standard works such as Houben-Weyl,Methoden der Organischen Chemie [Methods of organic chemistry],Georg-Thieme-Verlag, Stuttgart), and in particular under reactionconditions which are known and suitable for the said reactions. Variantswhich are known per se but not mentioned here in more detail, can alsobe utilized here.

If desired, the starting materials can also be formed in situ, in such away that they are not isolated from the reaction mixture but immediatelyconverted further into the compounds of the formula I.

The novel compounds of the formula II comprise compounds of the partformulae IIa, IIb and IIc:

    R.sup.1 --A.sup.2 --R.sup.2                                IIa

    R.sup.1 --A.sup.1 --A.sup.2 --R.sup.2                      IIB

    R.sup.1 --A.sup.1 --Z.sup.1 --A.sup.2 --R.sup.2            IIc

Those of the part formulae IIb and IIc, especially IIb, are preferredamongst these.

Part formula IIa comprises preferred compounds of t he formulae IIaa toIIae:

    R.sup.1 --Cy--R.sup.2                                      IIa

    R.sup.1 --Dio--R.sup.2                                     IIab

    R.sup.1 --Phe--R.sup.2                                     IIac

    R.sup.1 --Pyd--R.sup.2                                     IIad

    R.sup.1 --Pyr--R.sup.2                                     IIae

In compounds of the part formula IIa, the sum of the number of C atomsin the two groups R¹ and R² is preferably at least 8.

Part formula IIb comprises preferred compounds of the formulae IIba toIlbf:

    R.sup.1 --Cy--Cy--R.sup.2                                  IIba

    R.sup.1 --Cy--Dio--R.sup.2                                 IIbb

    R.sup.1 --Cy--Phe--R.sup.2                                 IIbc

    R.sup.1 --Cy--Pyd--R.sup.2                                 IIbd

    R.sup.1 --Cy--Pyr--R.sup.2                                 IIbe

    R.sup.1 --Dio--Phe--R.sup.2                                IIbf

Those of the part formulae IIba and IIbc, especially IIba, areparticularly preferred amongst these.

Part formula IIc comprises preferred compounds of the formulae IIca toIIcf:

    R.sup.1 --Cy--Z.sup.1 --Cy--R.sup.2                        IIca

    R.sup.1 --Cy--Z.sup.1 --Dio--R.sup.2                       IIcb

    R.sup.1 --Cy--Z.sup.1 --Phe--R.sup.2                       IIcc

    R.sup.1 --Cy--Z.sup.1 --Pyd--R.sup.2                       IIcd

    R.sup.1 --Cy--Z.sup.1 --Pyr--R.sup.2                       IIce

    R.sup.1 --Dio--Z.sup.1 --Phe--R.sup.2                      IIef

In the compounds of the part formula IIc, Z¹ is preferably --CO--O--,--O--CO-- or --CH₂ CH₂ --.

In the compounds of the formulae II, A¹ is preferably unsubstitutedtrans-1,4-cyclohexylene, 1,4-bicyclo[2.2.2]octylene,trans-1,3-dioxane-2,5-diyl or trans-tetrahydropyran-2,5-diyl.trans-1,4-Cyclohexylene is particularly preferred. A² is preferablyunsubstituted 1,4-phenylene, pyridine-2,5-diyl, pyrimidine-2,5-diyl ortrans-1,4-cyclohexylene. Particularly preferred meanings of A² aretrans-1,4-cyclohexylene and 1,4-phenylene. Z¹ is preferably a singlebond.

The novel compounds of the formula III comprise compounds of the partformulae IIIa to IIIe:

    R.sup.1 --A.sup.3 --Z.sup.2 --A--R.sup.2                   IIIa

    R.sup.1 --A.sup.3 --Z.sup.2 --A--Z.sup.1 --A.sup.2 --R.sup.2IIIb

    R.sup.1 --A--Z.sup.2 --A.sup.3 --Z.sup.1 --A.sup.2 --R.sup.2IIc

    R.sup.1 --A.sup.3 --Z.sup.2 --A--Z.sup.1 --A.sup.2 --Z.sup.1 --A.sup.2 --R.sup.2                                                 IIId

    R.sup.1 --A--Z.sup.2 --A.sup.3 --Z.sup.1 --A.sup.2 --Z.sup.1 --A.sup.2 --R.sup.2                                                 IIe

Those of the part formulae IIIa, IIIb and IIIc, but especially IIIa, areparticularly preferred amongst these.

Part formula IIIa comprises preferred compounds of the formulae IIIaa toIIIac:

    R.sup.1 --Phe--Z.sup.2 --A--R.sup.2                        IIIaa

    R.sup.1 --Pyd--Z.sup.2 --A--R.sup.2                        IIIab

    R.sup.1 --Pyr--Z.sup.2 --A--R.sup.2                        IIIac

Those of the part formula IIIaa are particularly preferred amongstthese. In the compounds of the part formula II Ia, Z² is preferably--CO--O--, --O--CO--, --CH₂ CH₂ -- or a single bond, a single bond beingparticularly preferred.

Part formula IIIb comprises preferred compounds of the formulae IIIba toIIIbg:

    R.sup.1 --Phe--Z.sup.2 --A--Z.sup.1 --Phe--R.sup.2         IIIba

    R.sup.1 --Phe--Z.sup.2 --A--Z.sup.1 --Cy--R.sup.2          IIIbb

    R.sup.1 --Phe--Z.sup.2 --A--Z.sup.1 --Dio--R.sup.2         IIIbc

    R.sup.1 --Pyd--Z.sup.2 --A--Z.sup.1 --Phe--R.sup.2         IIIbd

    R.sup.1 --Pyd--Z.sup.2 --A--Z.sup.1 --Cy--R.sup.2          IIIbe

    R.sup.1 --Pyr--Z.sup.2 --A--Z.sup.1 --Phe--R.sup.2         IIIbf

    R.sup.1 --Pyr--Z.sup.2 --A--Z.sup.1 --Cy--R.sup.2          IIIbg

Those of the part formulae IIIba and IIIbb are particularly preferredamongst these.

Part formula IIIc comprises preferred compounds of the formulae IIIca toIIIcg:

    R.sup.1 --A--Z.sup.2 --Phe--Z.sup.1 --Phe--R.sup.2         IIIca

    R.sup.1 --A--Z.sup.2 --Phe--Z.sup.1 --Cy--R.sup.2          IIIcb

    R.sup.1 --A--Z.sup.2 --Phe--Z.sup.1 --Dio--R.sup.2         IIIcc

    R.sup.1 --A--Z.sup.2 --Pyd--Z.sup.1 --Phe--R.sup.2         IIIcd

    R.sup.1 --A--Z.sup.2 --Pyd--Z.sup.1 --Cy--R.sup.2          IIIce

    R.sup.1 --A--Z.sup.2 --Pyr--Z.sup.1 --Phe--R.sup.2         IIIcf

    R.sup.1 --A--Z.sup.2 --Pyr--Z.sup.1 --Cy--R.sup.2          IIIcg

Those of the part formulae IIIca and IIIcb are particularly preferredamongst these.

In the compounds of the part formulae IIIb and IIIc, preferably at leastone of the groups Z¹ and Z² is a single bond an d the other group Z¹ orZ² is a group selected from the group comprising --CO--O--, --O--CO--,--CH₂ CH₂ -- and a single bond. Corresponding compounds with Z¹ =Z² =asingle bond are particularly preferred.

In the compounds of the formula III, A¹ is preferably --A--Z² --A³ --. Ais preferably pyridine-2,5-diyl or pyrimidine-2,5-diyl. A³ is preferably1,4-phenylene, pyridine-2,5-diyl or pyrimidine-2,5-diyl, particularlypreferably 1,4-phenylene. A² is preferably 1,4-phenylene,trans-1,4-cyclohexylene, trans-1,3-dioxane-2,5-diyl ortrans-tetrahydropyran-2,5-diyl, especially preferably 1,4-phenylene ortrans-1,4-cyclohexylene. Z¹ and Z² are preferably single bonds,--CO--O--, --O--CO-- or --CH₂ CH₂, and preferably at most one group Z¹and Z² is a grouping other than a single bond. p is preferably 0 or 1,particularly preferably 0.

The novel compounds of the formula IV comprise compounds of the partformulae IVa and IVb (with two rings) and IVc to IVe (with three rings):

    R.sup.1 --A.sup.1 --A.sup.2 --R.sup.2                      IVa

    R.sup.1 --A.sup.1 --Z.sup.1 --A.sup.2 --R.sup.2            IVb

    R.sup.1 --A.sup.1 --A.sup.1 --A.sup.2 --R.sup.2            IVc

    R.sup.1 --A.sup.1 --Z.sup.1 --A.sup.1 --A.sup.2 --R.sup.2  IVd

    R.sup.1 --A.sup.1 --A.sup.1 --Z.sup.1 --A.sup.2 --R.sup.2  IVe

Those of the formulae IVb, IVc, IVd and IVe, especially of the formulaeIVc and IVe, are preferred amongst these.

For the sake of simplicity, in the preceding and following text, PheXdesignates 1,4-phenylene which is substituted by one or two F atoms.

Part formula IVa comprises preferred compounds of the formulae IVaa toIVad:

    R.sup.1 --Cy--PheX--R.sup.2                                IVaa

    R.sup.1 --Dio--PheX--R.sup.2                               IVab

    R.sup.1 --Dit--PheX--R.sup.2                               IVac

    R.sup.1 --Cy--Phe--R.sup.2                                 IVad

Those of the formulae IVaa and IVad are particularly preferred amongstthese.

Part formula IVb comprises preferred compounds of the formulae IVba toIVbd:

    R.sup.1 --Cy--Z.sup.1 --PheX--R.sup.2                      IVba

    R.sup.1 --Dio--Z.sup.1 --PheX--R.sup.2                     IVbb

    R.sup.1 --Dit--Z.sup.1 --PheX--R.sup.2                     IVbc

    R.sup.1 --Cy--Z.sup.1 --Phe--R.sup.2                       IVbd

Those of the formulae IVba and IVbd are particularly preferred amongstthese.

Part formula IVc comprises preferred compounds of the formulae IVca toIVce:

    R.sup.1 --Cy--Cy--Phe--R.sup.2                             IVca

    R.sup.1 --Cy--Cy--PheX--R.sup.2                            IVcb

    R.sup.1 --Dio--Cy--Phe--R.sup.2                            IVcc

    R.sup.1 --Dit--Cy--Phe--R.sup.2                            IVcd

    R.sup.1 --A.sup.1 --Cy--PheX--R.sup.2                      IVce

Those of the formulae IVca and IVcb are particularly preferred amongstthese.

Part formula IVd comprises preferred compounds of the formulae IVda toIVdh:

    R.sup.1 --Cy--Z.sup.1 --Cy--Phe--R.sup.2                   IVda

    R.sup.1 --Cy--Z.sup.1 --Cy--PheX--R.sup.2                  IVdb

    R.sup.1 --A.sup.1 --Z.sup.1 --Cy--Phe--R.sup.2             IVdc

    R.sup.1 --Cy--Z.sup.1 --A.sup.1 --Phe--R.sup.2             IVdd

    R.sup.1 --Cy--Z.sup.1 --A.sup.1 --PheX--R.sup.2            IVde

    R.sup.1 --A.sup.1 --Z.sup.1 --Cy--PheX--R.sup.2            IVdf

    R.sup.1 --Cy--CH.sub.2 CH.sub.2 --Cy--Phe--R.sup.2         IVdg

    R.sup.1 --Cy--CH.sub.2 CH.sub.2 --Cy--PheX--R.sup.2        IVdh

Those of the formulae IVda, IVdb, IVdg and IVdh are particularlypreferred amongst these.

Part formula IVe comprises preferred compounds of the formulae IVea toIVej:

    R.sup.1 --Cy--Cy--Z.sup.1 --Phe--R.sup.2                   IVea

    R.sup.1 --Cy--Cy--Z.sup.1 --PheX--R.sup.2                  IVeb

    R.sup.1 --A.sup.1 --Cy--Z.sup.1 --Phe--R.sup.2             IVec

    R.sup.1 --A.sup.1 --Cy--Z.sup.1 --PheX--R.sup.2            IVed

    R.sup.1 --Cy--A.sup.1 --Z.sup.1 --Phe--R.sup.2             IVee

    R.sup.1 --Cy--A.sup.1 --Z.sup.1 --PheX--R.sup.2            IVef

    R.sup.1 --Cy--Cy--CH.sub.2 CH.sub.2 --Phe--R.sup.2         IVeg

    R.sup.1 --Cy--Cy--CH.sub.2 CH.sub.2 --PheX--R.sup.2        IVeh

    R.sup.1 --Cy--Cy--COO--Phe--R.sup.2                        IVei

    R.sup.1 --Cy--Cy--COO--PheX--R.sup.2                       IVej

Those of the formulae IVea,IVeb, IVeg and IVei are particularlypreferred amongst these.

Z¹ in the compounds of the part formulae IVb, IVd and IVe is preferably--CH₂ CH₂ --, --COO-- or --OCO--, and also preferably a single bond.

A¹ is preferably 1,4-cyclohexylene and A² is 1,4-phenylene which isunsubstituted or substituted by 2 fluorine atoms in the 2- and3-positions. m is 1 or 2, preferably 2.

R² in the formula IV and the corresponding part formulae is aperfluoroalkyl group of the formula --X'--Q'--Y'--R⁵ with the meaningsalready given.

R¹ in the formula IV and one of the radicals R¹ or R² in the formulae I,II and III are preferably alkyl, alkoxy, alkoxy carbonyl or oxaalkylpreferably having 2-12 C atoms. Alkyl is particularly preferred.

The alkyl radicals in the groups R¹ and/or R² can be straight-chain orbranched- Preferably, they are straight-chain, have2,3,4,5,6,7,8,9,10,11 or 12 C atoms and accordingly are preferablyethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl,undecyl or dodecyl, and also methyl, tridecyl, tetradecyl or pentadecyl.

If R¹ and/or R² in the compounds of the formulae I, II, III and IV arealkyl radicals in which, for example, one CH₂ group can also be replacedby an O atom (alkoxy or oxaalkyl), they can be straight-chain orbranched. Preferably, they are straight-chain, have 2, 3, 4, 5, 6, 7, 8,9, 10, 11 or 12 C atoms and accordingly are preferably ethyl, propyl,butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl or dodecyl,ethoxy, propoxy, butoxy, pentoxy, hexoxy, heptoxy, octoxy, nonoxy,decyloxy or undecyloxy, or 2-oxapropyl (=methoxymethyl), 2-(=ethoxymethyl) or 3-oxabutyl (=2-methoxyethyl), 2-, 3- or 4-oxapentyl,2-, 3-, 4- or 5-oxahexyl, 2-, 3-, 4-, 5- or 6-oxaheptyl, 2-, 3-, 4-, 5-,6- or 7-oxaoctyl, 2-, 3-, 4-, 5-, 6-, 7- or 8-oxanonyl or 2-, 3-, 4-,5-, 6-, 7-, 8- or 9-oxadecyl.

Compounds of the formulae I, II, III and IV with branched wing groupsmay sometimes be important because of higher solubility in the usualliquid-crystalline base materials, in particular as chiral dopingmaterials if they are optically active. Branched chains of this typecontain as a rule not more than one chain branching, but multiplebranching is possible.

Preferred branched radicals R¹ and R² are isopropyl, 2-butyl(=1-methylpropyl), isobutyl (=2-methylpropyl), 2-methylbutyl, isopentyl(=3-methylbutyl), 2-methylpentyl, 3-methylpentyl, 2-ethylhexyl,2-propylpentyl, 2-octyl, isopropoxy, 2-methylpropoxy, 2-methylbutoxy,3-methylbutoxy, 2-methylpentoxy, 3-methylpentoxy, 2-ethylhexoxy,1-methylhexoxy, 2-octyloxy, 2-oxa-3-methytbutyl, 3-oxa-4-methylpentyl,4-methylhexyl, 2-nonyl, 2-decyl, 2-dodecyl, 6-methyloctoxy,6-methyloctanoyloxy, 5-methylheptyloxycarbonyl, 2-methylbutyryloxy,3-methylvaleryloxy, 4-methylhexanoyloxy, 2-chloropropionyloxy,2-chloro-3-methylbutyryloxy, 2-chloro-4-methylvaleryloxy,2-chloro-3-methylvaleryloxy, 2-methyl-3-oxapentyl and 2-methyl-oxahexyl.

If the compounds of the formulae I, II, III and IV contain an asymmetricC atom, these formulae comprise racemates and also optically activeenantiomers and enantiomer mixtures.

A smaller group of particularly preferred compounds of the formulae II,III or IV is that of the following formulae 14-43:

    Alkyl--Cy--COO--Phe--CH.sub.2 CH.sub.2 --R.sub.F           14

    Alkyl--Cy--Cy--CH.sub.2 CH.sub.2 --R.sub.F                 15

    Alkyl--Cy--Cy--R.sub.F                                     16

    Alkyl--Cy--Cy--CH.sub.2 CH.sub.2 --Phe--CH.sub.2 CH.sub.2 --R.sub.F 17

    Alkyl--Cy--Cy--Phe--CH.sub.2 CH.sub.2 --R.sub.F            18

    Alkyl--Cy--Cy--COO--Phe--R.sub.F                           19

    Alkyl--Cy--COO--Phe--R.sub.F                               20

    Alkyl--Cy--COO--Phe--OR.sub.F                              21

    Alkyl--Cy--Cy--COO--Phe--OR.sub.F                          22

    Alkyl--Cy--Cy--CH.sub.2 CH.sub.2 --Phe--OR.sub.F           23

    Alkyl--Cy--CH.sub.2 CH.sub.2 --Phe--OR.sub.F               24

    Alkyl--Cy--Cy--Phe--OR.sub.F                               25

    Alkyl--Cy--CH.sub.2 CH.sub.2 --Cy--Phe-OR.sub.F            26

    Alkyl--Cy--Cy--CH.sub.2 CH.sub.2 --Phe--R.sub.F            27

    Alkyl--Cy--Cy--Phe--R.sub.F                                28

    Alkyl--Cy--Cy--Phe--CO--R.sub.F                            29

    Alkyl--Cy--CH.sub.2 CH.sub.2 --Phe--CO--R.sub.F            30

    Alkyl--Cy--Cy--CH.sub.2 CH.sub.2 --Phe--CO--R.sub.F        31

    Alkyl--Cy--CH.sub.2 CH.sub.2 --Cy--Phe--CO--R.sub.F        32

    Alkyl--Cy--Cy--COO--Phe--R.sub.F                           33

    Alkyl--Pyr--Phe--CH═CH--COOCH.sub.2 --R.sub.F          34

    Alkyl--Cy--Phe--OR.sub.F                                   35

    R.sub.F --Cy--Phe--Alkyl                                   36

    R.sub.F --Cy--Phe--Alkoxy                                  37

    Alkyl--Cy--Phe--CH═CH--R.sub.F                         38

    Alkyl--Pyr--Phe--CH═CH--R.sub.F                        39

    Alkyl--Cy--Phe--CH.sub.2 CH.sub.2 --R.sub.F                40

    Alkyl--Pyd--Phe--CH.sub.2 CH.sub.2 --R.sub.F               41

    Alkyl--Pyr--Phe--OR.sub.F                                  42

    Alkyl--Cy--Phe--CO--R.sub.F                                43

R_(F) here has the meaning given.

The novel compounds of the formulae II, III and IV are all prepared bymethods known per se, such as are described in the literature (forexample in the standard works such as Houben-Weyl, Methoden derOrganischen Chemie [Methods of organic chemistry], Georg Thieme Verlag,Stuttgart, or in Synthesis of Fluoroorganic Compounds, edited by I. L.Knunyants and G. G. Jakobsen, Springer Verlag, 1985), and in particularunder reaction conditions which are known and suitable for the saidreactions. It is also possible here to utilize variants which are knownper se and not mentioned here in more detail.

Thus, fluorine compounds of the formulae I, II, III and IV can beprepared, for example, by reacting corresponding hydroxy compounds in anautoclave under pressure with tetrafluoroethene the presence of dioxane,sodium and DMF.

Another possibility is, in a corresponding compound of the formula I,II, III or IV, in which Br takes the place of R², to exchange the Bratom for a --CO--R_(F) radical by reaction with butyllithium and analkyl perfluoroalkane carboxylate at low temperatures. If required, thecarbonyl group can then be converted into a CF₂ group by means ofdiethylaminosulfur trifluoride.

In a further possible method of preparation, corresponding hydroxycompounds are esterified with trifluoroacetic acid and then converted toan --OR_(F) group by means of sulfur tetrafluoride and hydrofluoricacid.

Further possible preparation methods can be taken by a person skilled inthe art from the quoted Literature or from the examples which follow.

The liquid-crystalline phases according to the invention consist of 2 to25, preferably 3 to 15 components which include at Least one compound ofthe formulae I, II, III or IV. The other constituents are preferablyselected from the nematic or nematogenic substances, in particular theknown substances, from the series of the azoxybenzenes,benzylideneanilines, biphenyls, terphenyls, phenyl or cyclohexylbenzoates, phenyl or cyclohexyl cyclohexanecarboxylates,phenylcyclohexanes, cyclohexylbiphenyls, cyclohexylcyclohexanes,cyclohexylnaphthalenes, 1,4-bis-cyclohexylbenzenes,4,4'-bis-cyclohexylbiphenyls, phenyl- or cyclohexyl-pyrimidines, phenyl-or cyclohexyldioxanes, phenyl- or cyclohexyl-1,3-dithianes,1,2-biscyclohexylethanes, 1,2-bis-phenylethanes,1-phenyl-2-cyclohexylethanes, optionally halogenated stilbenes, benzylphenyl ethers, tolanes and substituted cinnamic acids.

The most important compounds which can be used as constituents of suchliquid-crystalline phases can be characterized by the formula V

    R'--L--G--E--R"                                            V

wherein L and E each are a carbocyclic or heterocyclic ring system fromthe group comprising 1,4-disubstituted benzene and cyclohexane rings,4,4'-disubstituted biphenyl, phenylcyclohexane and cyclohexylcyclohexanesystems, 2,5-disubstituted pyrimidine and 1,3-dioxane rings,2,6-disubstituted naphthalene, di- and tetra-hydronaphthalene,quinazoline and tetrahydroquinazoline,

    ______________________________________                                        --CH═CH--    --N(O)═N--                                               --CH═CY--    --CH═N(O)--                                              --C.tbd.C--      --CH.sub.2 --CH.sub.2 --                                     --CO--O--        --CH.sub.2 --O--                                             --CO--S--        --CH.sub.2 --S--                                             --CH═N--     --COO--Phe--COO--                                            ______________________________________                                    

or a C--C single bond, Y is halogen, preferably chlorine, or --CN, andR' and R" are alkyl, alkoxy, alkanoyloxy or alkoxycarbonyloxy having upto 18, preferably up to 8, carbon atoms, or one of these radicals canalso be CN, NC, NO₂, CF₃, F, Cl or Br.

In most of these compounds, R' and R" are different, one of theseradicals being in most cases an alkyl group or alkoxy group. However,other variants of the envisaged substituents are also usual. Many suchsubstances or even mixtures thereof are commercially available. All ofthese substances can be prepared by methods known from the literature.

The phases according to the invention contain about 0.1 to 99%,preferably 10 to 95%, of one or more compounds of the formula I.Dielectrics according to the invention, which contain 0.1 to 40%,preferably 0.5 to 30%, of one or more compounds of the formulae I, II,III and/or IV, are also preferred.

Compounds of a formulae I, II, III, and IV with an optically active winggroup are suitable as components of nematic liquid-crystalline phasesfor avoiding reverse twist and for improving the elastic constants.

Optically active compounds of the formulae I, II, III and IV, are alsosuitable as components of chirally tilted smectic liquid-crystallinephases.

In addition to chiral compounds of the formulae I, II, III or IV, thesephases contain, in the achiral base mixture, at least one componentwhich shows negative anisotropy or a small amount of positive dielectricanisotropy.

Compounds containing the structural element A, B or C are suitable asfurther components showing negative dielectric anisotropy. ##STR1##

Preferred compounds of this type are of the formulae VIa, VIb and VIc:##STR2##

R' and R" each are preferably straight-chain alkyl or alkoxy groups eachhaving 2 to 10 C atoms. Q¹ and Q² each are 1,4-phenylene,trans-1,4-cyclohexylene, 4,4'-biphenylyl, 4-(trans-4-cyclohexyl)-phenylor trans, trans-4,4'-bicyclohexyl, or one of the groups Q¹ and Q² arealso a single bond.

Q³ and Q⁴ each are 1,4-phenylene, 4,4'-biphenylyl ortrans-1,4-cyclohexylene. One of the groups Q³ and Q⁴ can also be1,4-phenylene in which at least one CH group is replaced by N. R'" is anoptically active radical with an asymmetric carbon atom of the structure##STR3## Particularly preferred compounds of the formula VI c are thoseof the formula VI c': ##STR4## Wherein A 1,4-phenylene ortrans-1,4-cyclohexylene and n is 0 or 1.

The dielectrics according to the invention are prepared in aconventional manner per se. As a rule, the components are dissolved inone another, advantageously elevated temperature.

The Liquid-crystalline dielectrics according to the invention can bemodified by suitable additives in such a way that they can be used inall hitherto disclosed types of liquid crystal display elements.

Such additives are known to those skilled in the art and are extensivelydescribed in the literature. For example, it is possible to addconductivity salts, preferably ethyl-dimethyl-dodecyl-ammonium4-hexyloxybenzoate, tetrabutylammonium tetraphenylboranate or complexsalts of crown ethers (compare, e.g., I. Hallet et al., Mol. Cryst.Liq.Cryst. Volume 24, pages 249-258 (1973)), for improving the conductivity,dichroic dyes for the preparation of coloured Guest-Host systems orsubstances for altering the dielectric anisotropy, the viscosity and/orthe orientation of the nematic phases. Such substances are described,for example, in German Offenlegungsschriften 2,209,127, 2,240,864,2,321,632, 2,338,281, 2,450,088, 2,637,430, 2,853,728 and 2,902,177.

The examples which follow are intended to explain the invention, withoutrestricting it. m.p.=melting point, c.p.=clear point. Percentage data inthe preceding and following text are percent by weight; all temperaturedata are given in degrees Celsius. "Workingup in the usual way" means:water is added, the mixture is extracted with methylene chloride andseparated, the organic phase is dried and evaporated and the product ispurified by crystallization, distillation and/or chromatography.

EXAMPLE 1

43.7 g of the known 4-(trans-4-propylcyclohexyl)phenol are dissolved in80 ml of anhydrous dioxane, and 1.2 g of sodium (as a 50% suspension inxylene) are added under a dry atmosphere. After stirring for 3 hours, 40ml of anhydrous dimethylformamide are added and the mixture istransferred into an autoclave which is flushed several times withnitrogen and then with tetrafluoroethene from a stock gas cylinder. Thetetrafluoroethene pressure is raised to 2.7 bar, the feed to the gascylinder is interrupted, and the autoclave is intensively shaken. Assoon as the pressure has fallen to 2.0 bar, it is raised again to 2.7bar. This is continued until the reaction stops. The contents of theautoclave are stirred into 500 ml of a 10% sodium hydroxide solution.The mixture is extracted several times with dichloromethane. Afterwashing with water, the organic phase is freed of solvent bydistillation. The residue is subjected to separation by columnchromatography (silica gel/toluene). After removal of the solvent, themain fraction is distilled in a bulb tube. This gives4-(trans-4-propylcyclohexyl)-1-(1,1,2,2-tetrafluoroethoxy)-benzene m.p.6° (c.P. -20°).

The following are prepared analogously:4-(trans-4-Methyl-cyclohexyl)-1-(1,1,2,2-tetrafluoroethoxy)-benzene

4-(trans-4-Ethyl-cyclohexyl-1-(1,1,2,2-tetrafluoroethoxy)benzene

4-(trans-4-Butyl-cyclohexyl-1-(1,1,2,2-tetrafluoroethoxy)benzene

4-(trans-4-Pentyl-cyclohexyl-1-(1,1,2,2-tetrafluoroethoxy)benzene

4-(trans-3-Hexyl-cyclohexyl-1-(1,1,2,2-tetrafluoroethoxy)benzene

4-(trans-4-Heptyl-cyclohexyl-1-(1,1,2,2-tetrafluoroethoxy)benzene

4-(trans-4-Octyl-cyclohexyl-1-(1,1,2,2-tetrafluoroethoxy)benzene

4-(trans-4-Nonyl-cyclohexyl-1-(1,1,2,2-tetrafluoroethoxy)benzene

4-(trans-4-Decyl-cyclohexyl-1-(1,1,2,2-tetrafluoroethoxy)benzene

4-Methyl-1-(1,1,2,2-tetrafluoroethoxy)-benzene

4-Ethyl-1-(1,1,2,2-tetrafluoroethoxy)-benzene

4-Butyl-1-(1,1,2,2-tetrafluoroethoxy)-benzene

4-Pentyl-1-(1,1,2-2-tetrafluoroethoxy)-benzene

4-Hexyl-1-(1,1,2,2-tetrafluoroethoxy)-benzene

4-Heptyl-1-(1,1,2,2-tetrafluoroethoxy)-benzene

4-Octyl-1-(1,1,2,2-tetrafluoroethoxy)-benzene

4-Nonyl-1-(1,1,2,2-tetrafluoroethoxy)-benzene

4-Decyl-1-(1,1,2,2-tetrafluoroethoxy)-benzene

EXAMPLE 2

11.1 g of 4-(trans-4-propylcyclohexyl)-cyclohexanone dissolved in 20 mlof diethyl ether are added dropwise at -35° to a suspension of 23.5 g ofperfluorohexylmagnesium iodide in 100 ml of diethyl ether. After 2hours, the mixture is worked up in the usual way and the resulting1-perfluorohexyl-4-(trans-4-propytcyclohexyl)cyclohexanol is dissolvedin 40 ml of dichloromethane and 16 ml of pyridine. This solution isadded dropwise at 0° with stirring to a solution of 2.6 ml ofdiethylaminosulfur trifluoride in 40 mL of dichloromethane.

After 1 hour, the mixture is worked up in the usual way and the crudeproduct is dissolved in toluene, and the solution is filtered oversilica gel and evaporated to dryness. The residue is dissolved inglacial acetic acid, hydrogenated at normal pressure and roomtemperature in the presence of Pt catalyst and worked up in the usualway. After further purification by chromatography and fractionalcrystallization, this givestrans,trans-4-perfluorohexyl-4'-propylcyclohexylcyclohexane, m.p. 48°(c.p. -30°).

The following are prepared analogously:

trans,trans-4-Perfluorohexyl-4'-ethylcyclohexylcyclohexane

trans-trans-4-Perfluorohexyl-4'-butylcyclohexylcyclohexane

trans-trans-4-Perfluorohexyl-4'-pentylcyclohexylcyclohexane

trans,trans-4-Perfluorohexyl-4'-heptylcyclohexylcyclohexane

trans,trans-4-Perfluorobutyl-4'-ethylcyclohexylcyclohexane

trans,trans-4-Perfluorobutyl-4'-propylcyclohexylcyclohexane

trans,trans-4-Perfluorobutyl-4'-butylcyclohexylcyclohexane

trans,trans-4-Perfluorobutyl-4'-pentylcyclohexylcyclohexane

trans,trans-4-Perfluorobutyl-4'-heptylcyclohexylcyclohexane

trans,trans-4-Perfluoroethyl-4'-ethylcyctohexylcyclohexane

trans,trans-4-Perfluoroethyl-4'-propylcyclohexylcyclohexane

trans,trans-4-Perfluoroethyl-4'-butylcyclohexylcyclohexane

trans,trans-4-Perfluoroethyl-4'-pentylcyclohexylcyclohexane

trans-trans-4-Perfluoroethyl-4'-heptylcyclohexylcyclohexane

4-(trans-4-Perfluoroethylcyclohexyl)-1-ethylbenzene

4-(trans-4-Perfluoroethylcyclohexyl)-1-propylbenzene

4-(trans-4-Perfluoroethylcyclohexyl)-1-butylbenzene

4-(trans-4-Perfluoroethylcyclohexyl)-1-pentylbenzene

4-(trans-4-Perfluoroethylcyclohexyl)-1-heptylbenzene

4-(trans-4-Perfluoroethylcyclohexyl)-1-methoxybenzene

4-(trans-4-Perfluoroethylcyclohexyl)-1-ethoxybenzene

4-(trans-4-Perfluoroethylcyclohexyl)-1-propoxybenzene

4-(trans-4-Perfluoroethylcyclohexyl)-1-butoxybenzene

4-(trans-4-Perfluoroethylcyclohexyl)-1-pentoxybenzene

4-(trans-4-Perfluoroethylcyclohexyl)-1-hexoxybenzene

4-(trans-4-Perfluoroethylcyclohexyl)-1-octoxybenzene

4-(trans-4-Perfluorobutylcyclohexyl)-1-ethylbenzene

4-(trans-4-Perfluorobutylcyclohexyl)-1-propylbenzene

4-(trans-4-Perfluorobutylcyclohexyl)-1-butylbenzene

4-(trans-4-Perfluorobutylcyclohexyl)-1-pentylbenzene

4-(trans-4-Perfluorobutylcyclohexyl)-1-heptylbenzene

4-(trans-4-Perfluorobutylcyclohexyl)-1-methoxybenzene

4-(trans-4-Perfluorobutylcyclohexyl)-1-ethoxybenzene

4-(trans-4-Perfluorobutylcyclohexyl)-1-propoxybenzene

4-(trans-4-Perfluorobutylcyclohexyl)-1-butoxybenzene

4-(trans-4-Perfluorobutylcyclohexyl)-1-pentoxybenzene

4-(trans-4-Perfluorobutylcyclohexyl)-1-hexoxybenzene

4-(trans-4-Perfluorobutylcyclohexyl)-1-octoxybenzene

4-(trans-4-Perfluorohexylcyclohexyl)-1-ethylbenzene

4-(trans-4-Perfluorohexylcyclohexyl)-1-propylbenzene

4-(trans-4-Perfluorohexylcyclohexyl)-1-butylbenzene

4-(trans-4-Perfluorohexylcyclohexyl)-1-pentylbenzene

4-(trans-4-Perfluorohexylcyclohexyl)-1-heptylbenzene

4-(trans-4-Perfluorohexylcyclohexyl)-1-methoxybenzene

4-(trans-4-Perfluorohexylcyclohexyl)-1-ethoxybenzene

4-(trans-4-Perfluorohexylcyclohexyl)-1-propoxybenzene

4-(trans-4-Perfluorohexylcyclohexyl)-1-butoxybenzene

4-(trans-4-Perfluorohexylcyclohexyl)-1-pentoxybenzene

4-(trans-4-Perfluorohexylcyclohexyl)-1-hexoxybenzene

4-(trans-4-Perfluorohexylcyclohexyl)-1-octoxybenzene

4-(trans-Perfluorooctylcyclohexyl)-1-ethylbenzene

4-(trans-Perfluorooctylcyclohexyl)-1-propylbenzene

4-(trans-Perfluorooctylcyclohexyl)-1-butylbenzene

4-(trans-Perfluorooctylcyclohexyl)-1-pentylbenzene

4-(trans-Perfluorooctylcyclohexyl)-1-heptylbenzene

4-(trans-Perfluorooctylcyclohexyl)-1-methoxybenzene

4-(trans-Perfluorooctylcyclohexyl)-1-ethoxybenzene

4-(trans-Perfluorooctylcyclohexyl)-1-propoxybenzene

4-(trans-Perfluorooctylcyclohexyl)-1-butoxybenzene

4-(trans-Perfluorooctylcyclohexyl)-1-pentoxybenzene

4-(trans-Perfluorooctylcyclohexyl)-1-hexoxybenzene

4-(trans-Perfluorooctylcyclohexyl)-1-octoxybenzene

4-(trans-4-Perfluorodecylcyclohexyl)-1-ethylbenzene

4-(trans-4-Perfluorodecylcyclohexyl)-1-propylbenzene

4-(trans-4-Perfluorodecylcyclohexyl)-1-butylbenzene

4-(trans-4-Perfluorodecylcyclohexyl)-1-pentylbenzene

4-(trans-4-Perfluocodecylcyclohexyl)-1-heptylbenzene

4-(trans-4-Perfluorodecylcyclohexyl)-1-methoxybenzene

4-(trans-4-Perfluorodecylcyclohexyl)-1-ethoxybenzene

4-(trans-4-Perfluorodecylcyclohexyl)-1-propoxybenzene

4-(trans-4-Perfluorodecylcyclohexyl)-1-butoxybenzene

4-(trans-4-Perfluorodecylcyclohexyl)-1-pentoxybenzene

4-(trans-4-Perfluorodecylcyclohexyl)-1-hexoxybenzene

4-(trans-4-Perfluorodecylcyclohexyl)-1-octoxybenzene

EXAMPLE 3

A mixture of 10 g of r-1-cyano-cis-4-(p-bromophenyl)-1-butylcyclohexane,13 ml of perfluorohexylethylene, 3.5 ml of triethylamine, 50 ml ofacetonitrile, 0.1 g of Pd(II) acetate and 0.25 g of tri-o-tolylphosphineis heated under reflux for 72 hours. After cooling to 0°, the resultingcrystals are filtered off with suction, washed with acetonitrile andwater and recrystallized from acetonitrile. This givesE-1-perfluorohexyl-2-[p(4-cyano-4-butylcyclohexyl)-phenyl]-ethene, m.p.117°.

The following are prepared analogously:

E-1-Perfluorohexyl-2-[p-(trans-4-propylcyclohexyl)phenyl]ethene, m.p.45°

E-1-Perfluorohexyl-2-[p-(5-propylpyrimidin-2-yl)-phenyl]ethene, m.p.105°, c.p. 140°

E-1-Perfluorohexyl-2-[p-(5-heptylpyrimidin-2-yl)-phenyl]ethene, m.p.77°, c.p. 113°

EXAMPLE 4

Hydrogenation of 2.3 g ofE-1-perfluorohexyl-2-[p-(4-cyano-4-butylcyclohexyl)-phenyl]-ethene(Example 3) in 50 ml of tetrahydrofuran over 1 g of Pd/C-(5%) andrecrystallization of the resulting crude product from ethanol gives1-perfluorohexyl-2-[p-(4-cyano-4-butylcyclohexyl)-phenyl]-ethane, m.p.71°.

The following are prepared analogously:

1-perfluorohexyl-2-[p-(trans-4-propylcyclohexyl)-phenyl]-ethane, m.p.41°

1-perfluorohexyl-2-[p-(5-propylpyrimidin-2-yl)-phenyl]-ethane m.p. 69° ,c.p. 137°

EXAMPLE 5

38.7 g of the known 4-(5-heptylpyrimidin-2-yl)phenol are dissolved in 60ml of anhydrous dioxane, and 0.9 g of sodium (as a 50% suspension inxylene) is added under a dry atmosphere. After stirring for 3 hours, 20ml of anhydrous dimethylformamide are added and the mixture istransferred into an autoclave which is flushed several times withnitrogen and then with tetrafluoroethene from a stock gas cylinder. Thetetrafluoroethene pressure is raised to 2.7 bar, the feed to the gascylinder is interrupted and the autoclave is intensively shaken. As soonas the pressure has fallen to 2.0 bar, it is raised again to 2.7 bar.This is continued until the reaction stops. The contents of theautoclave are stirred into 500 ml of 10% sodium hydroxide solution. Themixture is extracted several times with dichloromethane. After washingwith water, the organic phase is freed of solvent by distillation. Theresidue is subjected to separation by column chromatography (silicagel/dichloromethane). After removal of the solvent, the main fraction isrecrystallized from ethanol. This gives4-(5-heptylpyrimidin-2-yl)-1-(1,1,2,2-tetrafluoroethoxy)-benzene, m.p.46° (c.p. 43°).

The following are prepared analogously:

4-(5-Ethylpyrimidin-2-yl)-1-(1,1,2,2-tetrafluoroethoxy)benzene

4-(5-Propylpyrimidin-2-yl)-1-(1,1,2,2-tetrafluoroethoxy)benzene

4-(5-Butylpyrimidin-2-yl)-1-(1,1,2,2-tetrafluoroethoxy)benzene

4-(5-Pentylpyrimidin-2-yl)-1-(1,1,2,2-tetrafluoroethoxy)benzene

4-(5-Hexylpyrimidin-2-yl)-1-(1,1,2,2-tetrafluoroethoxy)benzene

4-(5-Octylpyrimidin-2-yl)-1-(1,1,2,2-tetrafluoroethoxy)benzene

4-(5-Nonylpyrimidin-2-yl)-1-(1,1,2,2-tetrafluoroethoxy)benzene

4-(5-Decylpyrimidin-2-yl)-1-(1,1,2,2-tetrafluoroethoxy)benzene

EXAMPLE 6

A mixture if 11.9 g of p-(trans-4-propylcyclohexyl)trifluoroacetophenone[obtainable by reacting p-(trans-4-propylcyclohexyl)-bromobenzene withmethyl trifluoroacetate in the presence of butyllithium] and 10.5 mL ofdiethylaminosulfur trifluoride is stirred for 7 days 65°. After usualworking-up, this givestrans-1-p-perfluoroethylphenyl-4-propylcyclohexane, m.p. 18°, Δε+3.9.

The following are prepared analogously:

trans-1-p-Perfluoroethylphenyl-4-ethylcyclohexane

trans-1-p-Perfluoroethylphenyl-4-butylcyclohexane

trans-1-p-Perfluoroethylphenyl-4-pentylcyclohexane

trans-1-p-Perfluoroethylphenyl-4-heptylcyclohexane

EXAMPLE 7

A liquid-crystalline dielectric consisting of

24% of p-(trans-4-propylcyclohexyl)-benzonitrile,

36% of p-(trans-4-pentylcyclohexyl)-benzonitrile,

25% of p-(trans-4-heptylcyclohexyl)-benzonitrile and

15% of 4-cyano-4'-(trans-4-pentylcyclohexyl)-biphenyl

has a viscosity of 27 mPa.s at 20°. The viscosity values at 20° afterthe addition of in each case 10% of the compounds A-D according to theinvention to the above base mixture are shown in the following table:

    ______________________________________                                        Addition of 10% of the compound                                               according to the invention                                                                         A      B     C     D                                     ______________________________________                                        Viscosity in mPa · s at 20°                                                        25     26    22    26                                    ______________________________________                                         A: trans1-p-Perfluoroethylphenyl-4-propylcyclohexane                          B: trans,trans4-Perfluorohexyl-4propylcyclohexyl-cyclohexane                  C: 4(trans-4-Propylcyclohexyl-1-)1,1,2,2-tetrafluoroethoxy)-benzene           D: 1Perfluorohexyl-2-[p(5-propylpyrimidin-2-yl)-phenylethane             

EXAMPLE 8

10. 0 g of the known ethyl pentadecafluorooctanoate and 1.4 g of acetoneas a mixture are added, with exclusion of moisture, to 1.6 of freshlyprepared sodium methanolate and the resulting suspension is stirred for24 hours at room temperature. 2 N hydrochloric acid is then added untilthe mixture shows a neutral reaction. After extraction with three times30 ml of diethyl ether, the combined organic phases are washed with 30ml of water. The solution is dried with sodium sulfate, the solvent isevaporated and the residue is distilled at 30 mm Hg in a bulb tube. 7.7g of5,5,6,6,7,7,8,8,9,9,10,10,11,11,11-pentadecafluoroundecane-2,4-dionepass over at 140°-150° C.

EXAMPLE 9

A liquid-crystalline dielectric containing

23% of p-trans-4-propylcyclohexylbenzonitrile,

34% of p-trans-4-pentylcyclohexylbenzonitrile,

24% of p-trans-4-heptylcyclohexylbenzonitrile,

14% of 4-cyano-4'-(trans-4-pentylcyclohexyl)biphenyl and

5% of5,5,6,6,7,7,8,8,9,9,10,10,11,11,11-pentadecafluoroundecane-2,4-dione

is prepared.

EXAMPLE 10

0.1 mol of1-trans-4-(trans-4-propylcyclohexyl)cyclohexyl]-2-(p-trifluoromethylcarbonyloxyphenyl)-ethane(obtainable by esterification of trifluoroacetic acid with thecorresponding hydroxy compound), 25.0 g of sulfur tetrafluoride and 3.5g of anhydrous hydrofluoric acid are heated in an autoclave for 3 hoursat 150° and then for 12 hours at 175°. The mixture is then hydrolyzedunder alkaline conditions and worked up in the usual way. Afterpurification, this gives 1-[trans-4-(trans-4-propylcyclohexyl)-cyclohexyl]-2-(p-pentafluoroethoxyphenyl)-ethane.

The following are prepared analogously:

1-[trans-4-(trans-4-Methylcyclohexyl)cyclohexyl]-2-(p-pentafluoroethoxyphenyl)-ethane

1-[trans-4-(trans-4-Ethylcyclohexyl)cyclohexyl]-2-(p-pentafluoroethoxyphenyl)-ethane

1-[trans-4-(trans-4-Butylcyclohexyl)cyclohexyl]-2-(p-pentafluoroethoxyphenyl)-ethane

1-[trans-4-(trans-4-Pentylcyclohexyl)cyclohexyl]-2-(p-pentafluoroethoxyphenyl)-ethane

1-[trans-4-(trans-4-Hexylcyclohexyl)cyclohexyl]-2-(p-pentafluoroethoxyphenyl)-ethane

1-[trans-4-(trans-4-Heptylcyctohexyl)cyclohexyl]-2-(p-pentafluoroethoxyphenyl)-ethane

1-(trans-4-Methylcyclohexyl)-2-(p-pentafluoroethoxyphenyl)-ethane

1-(trans-4-Ethylcyclohexyl)-2-(p-pentafluoroethoxyphenyl)-ethane

1-(trans-4-Propylcyclohexyl)-2-(p-pentafluoroethoxyphenyl)-ethane

1-(trans-4-Butylcyclohexyl)-2-(p-pentafluoroethoxyphenyl)-ethane

1-trans-4-Pentylcyclohexyl)-2-(p-pentafluoroethoxyphenyl)-ethane

1-(trans-4-Hexylcyclohexyl)-2-(p-pentafluoroethoxyphenyl)-ethane

1-(trans-4-Heptylcyclohexyl)-2-(p-pentafluoroethoxyphenyl)-ethane

p-[trans-4-(trans-4-Methylcyclohexyl)cyclohexyl]-pentafluoroethoxybenzene

p-[trans-4-(trans-4-Ethylcyclohexyl)cyclohexyl]-pentafluoroethoxybenzene

p-[trans-4-(trans-4-Propylcyclohexyl)cyclohexyl]-pentafluoroethoxybenzene

p-[trans-4-(trans-4-Butylcyclohexyl)cyclohexyl]-pentafluoroethoxybenzene

p-[trans-4-(trans-4-Pentylcyclohexyl)cyclohexyl]-pentafluoroethoxybenzene

p-[trans-4-(trans-4-Hexylcyclohexyl)cyclohexyl]-pentafluoroethoxybenzene

p-[trans-4-(trans-4-Heptylcyclohexyl)cyclohexyl]-pentafluoroethoxybenzene

1-(trans-4-Methylcyclohexyl)-2-[trans-4-(p-pentafluoroethoxlphenyl)cyclohexyl)-ethane

1-(trans-4-Ethylcyclohexyl)-2-[trans-4-(p-pentafluoroethoxyphenyl)cyclohexyl)-ethane

1-(trans-4-Propylcyclohexyl)-2-[trans-4-(p-pentafluoroethoxyphenyl)cyclohexyl)-ethane

1-(trans-4-Butylcyclohexyl)-2-[trans-4-(p-pentafluoroethoxyphenyl)cyclohexyl)-ethane

1-(trans-4-Pentylcyclohexyl)-2-[trans-4(p-pentafluoroethoxyphenyl)cyclohexyl)-ethane

1-(trans-4-Hexylcyclohexyl)-2-[trans-4-(p-pentafluoroethoxyphenyl)cyclohexyl)-ethane

1-(trans-4-Heptylcyclohexyl)-2-[trans-4-(p-pentafluoroethoxyphenyl)cyclohexyl)-ethane

EXAMPLE 11

0.1 mol of a solution of n-butyllithium in hexane and then 0.1 mol ofethyl perfluorononanoate are added with stirring at -78° to a mixture of0.1 mol of4-[trans-4-(trans-4-propylcyclohexyl)-cyclohexyl]-bromobenzene, 150 mlof diethyl ether and 150 ml of tetrahydrofuran. After working up in theusual way, this gives4-[trans-4-(trans-4-propylcyclohexyl)cyclohexyl]phenyl perfluorooctylketone.

The following are prepared analogously:

4-[trans-4-(trans-4-Methylcyclohexyl)cyclohexyl]-phenyl perfluorooctylketone

4-[trans-4-(trans-4-Ethylcyclohexyl)cyclohexyl]-phenyl perfluorooctylketone

4-[trans-4-(trans-4-Butylcyclohexyl)cyclohexyl]-phenyl perfluorooctylketone

4-[trans-4-(trans-4-Pentylcyclohexyl)cyclohexyl]-phenyl perfluorooctylketone

4-[trans-4-(trans-4-Hexylcyclohexyl)cyclohexyl]-phenyl perfluorooctylketone

4-[trans-4-(trans-4-Heptylcyclohexyl)cyclohexyl]-phenyl perfluorooctylketone

4-[trans-4-(trans-4-Methylcyclohexyl)cyclohexyl]-phenyl perfluoroheptylketone

4-[trans-4-(trans-4-Ethylcyclohexyl)cyclohexyl]-phenyl perfluoroheptylketone

4-[trans-4-(trans-4-Propylcyclohexyl)cyclohexyl]-phenyl perfluoroheptylketone

4-[trans-4-(trans-4-Butylcyclohexyl)cyclohexyl]-phenyl perfluoroheptylketone

4-[trans-4-(trans-4-Pentylcyclohexyl)cyclohexyl]-phenyl perfluoroheptylketone

4-[trans-4-(trans-4-Hexylcyclohexyl)cyclohexyl]-phenyl perfluoroheptylketone

4-[trans-4-(trans-4-Heptylcyclohexyl)cyclohexyl]-phenyl perfluoroheptylketone

1-(trans-4-Methylcyclohexyl)-2-(4-perfluorooctylcarbonylphenyl)-ethane

1-(trans-4-Ethylcyclohexyl)-2-(4-perfluorooctylcarbonylphenyl)-ethane

1-(trans-4-Propylcyclohexyl)-2-(4-perfluorooctylcarbonylphenyl)-ethane

1-(trans-4-Butylcyclohexyl)-2-(4-perfluorooctylcarbonylphenyl)-ethane

1-(trans-4-Pentylcyclohexyl)-2-(4-perfluorooctylcarbonylphenyl)-ethane

1-(trans-4-Hexylcyclohexyl)-2-(4-perfluorooctylcarbonylphenyl)-ethane

1-(trans-4-Heptylcyclohexyl)-2-(4-perfluorooctylcarbonylphenyl)-ethane

1-(trans-4-Methylcyclohexyl)-2-(4-perfluoroheptylcarbonylphenyl)-ethane

1-(trans-4-Ethylcyclohexyl)-2-(4-perfluoroheptylcarbonylphenyl)-ethane

1-(trans-4-Propylcyclohexyl)-2-(4-perfluoroheptylcarbonylphenyl)-ethane

1-(trans-4-Butylcyclohexyl)-2-(4-perfluoroheptylcarbonylphenyl)-ethane

1-(trans-4-Pentylcyclohexyl)-2-(4-perfluoroheptylcarbonylphenyl)-ethane

1-(trans-4-Hexylcyclohexyl)-2-(4-perfluoroheptylcarbonylphenyl)-ethane

1-(trans-4-Heptylcyclohexyl)-2-(4-perfluoroheptylcarbonylphenyl)-ethane

1-[trans-4-(trans-4-Methylcyclohexyl)cyclohexyl]-2-(4-perfluorooctylcarbonylphenyl)-ethane

1-[trans-4-(trans-4-Ethylcyclohexyl)cyclohexyl]-2-(4-perfluorooctylcarbonylphenyl)-ethane

1-[trans-4-(trans-4-Propylcyclohexyl)cyclohexyl]-2-(4-perfluorooctylcarbonylphenyl)-ethane

1-[trans-4-(trans-4-Butylcyclohexyl)cyclohexyl]-2-(4-Perfluorooctylcarbonylphenyl)-ethane

1-[trans-4-(trans-4-Pentylcyclohexyl)cyclohexyl]-2-(4-perfluorooctylcarbonylphenyl)-ethane

1-[trans-4-(trans-4-Hexylcyclohexyl)cyclohexyl]-2-(4-Perfluorooctylcarbonylphenyl)-ethane

1-[trans-4-(trans-4-Heptylcyclohexyl)cyclohexyl]-2-(4-perfluorooctylcarbonylphenyl)-ethane

1-[trans-4-(trans-4-Methylcyclohexyl)cyclohexyl]-2-(4-perfluoroheptylcarbonylphenyl)-ethane

1-[trans-4-(trans-4-Ethylcyclohexyl)cyclohexyl]-2-(4-perfluoroheptylcarbonylphenyl)-ethane

1-[trans-4-(trans-4-Propylcyclohexyl)cyclohexyl]-2-(4-perfluoroheptylcarbonylphenyl)-ethane

1-[trans-4-(trans-4-Butylcyclohexyl)cyclohexyl]-2-(4-perfluoroheptylcarbonylphenyl)-ethane

1-[trans-4-(trans-4-Pentylcyclohexyl)cyclohexyl]-2-(4-perfluoroheptylcarbonylphenyl)-ethane

1-[trans-4-(trans-4-Hexylcyclohexyl)cyclohexyl]-2-(4-perfluoroheptylcarbonylphenyl)-ethane

1-[trans-4-(trans-4-Heptylcyclohexyl)cyclohexyl]-2-(4-perfluoroheptylcarbonylphenyl)-ethane

1-(trans-4-Methylcyclohexyl)-2-[trans-4-(4-perfluorooctylcarbonylphenyl)cyclohexyl]-ethane

1-(trans-4-Ethylcyclohexyl)-2-[trans-4-(4-perfluorooctylcarbonylphenyl)cyclohexyl]-ethane

1-(trans-4-Propylcyclohexyl)-2-[trans-4-(4-perfluorooctylcarbonylphenyl)cyclohexyl]-ethane

1-(trans-4-Butylcyclohexyl)-2-[trans-4-(4-perfluorooctylcarbonylphenyl)cyclohexyl]-ethane

1-(trans-4-Pentylcyclohexyl)-2-[trans-4-(4-perfluorooctylcarbonylphenyl)cyclohexyl]-ethane

1-(trans-4-Hexylcyclohexyl)-2-[trans-4-(4-perfluorooctylcarbonylphenyl)cyclohexyl]-ethane

1-(trans-4-Heptylcyclohexyl)-2-[trans-4-(4-perfluorooctylcarbonylphenyl)cyclohexyl]-ethane

1-(trans-4-Methylcyclohexyl)-2-[trans-4-(4-perfluoroheptylcarbonylphenyl)cyclohexyl]-ethane

1-(trans-4-Ethylcyclohexyl)-2-[trans-4-(4-perfluoroheptylcarbonylphenyl)cyclohexyl]-ethane

1-(trans-4-Propylcyclohexyl)-2-[trans-4-(4-perfluoroheptylcarbonylphenyl)cyclohexyl]-ethane

1-(trans-4-Butylcyclohexyl)-2-[trans-4-(4-perfluoroheptylcarbonylphenyl)cyclohexyl]-ethane

1-(trans-4-Pentylcyclohexyl)-2-[trans-4-(4-perfluoroheptylcarbonylphenyl)cyclohexyl]-ethane

1-(trans-4-Hexylcyclohexyl)-2-[trans-4-(4-perfluoroheptylcarbonylphenyl)cyclohexyl]-ethane

1-(trans-4-Heptylcyclohexyl)-2-[trans-4-(4-perfluoroheptylcarbonylphenyl)cyclohexyl]-ethane

EXAMPLE 12

A mixture of 0.1 mol of diethylaminosulfur trifluoride and 0.05 mol of4-[trans-4-(trans-4-propylcyclohexyl)-cyclohexyl]-phenyl perfluorooctylketone (prepared according to Example 11) is stirred for 7 days at 50°.CH₂ Cl₂ is then added, and the mixture is worked up in the usual way.After purification by chromatography, this gives4-[trans-4-(trans-4-propylcyclohexyl)cyclohexyl]-perfluorononyl-benzene.

The following are prepared analogously:

4-[trans-4-(trans-4-Methylcyclohexyl)cyclohexyl]-perfluorononyl-benzene

4-[trans-4-(trans-4-Ethylcyclohexyl)cyclohexyl]-perfluorononyl-benzene

4-[trans-4-(trans-4-Butylcyclohexyl)cyclohexyl]-perfluorononyl-benzene

4-[trans-4-(trans-4-Pentylcyclohexyl)cyclohexyl]-perfluorononyl-benzene

4-[trans-4-(trans-4-Hexylcyclohexyl)cyclohexyl]-perfluorononyl-benzene

4-[trans-4-(trans-4-Heptylcyclohexyl)cyclohexyl]-perfluorononyl-benzene

4-[trans-4-(trans-4-Methylcyclohexyl)cyclohexyl]-perfluorooctyl-benzene

4-[trans-4-(trans-4-Ethylcyclohexyl)cyclohexyl]-perfluorooctyl-benzene

4-[trans-4-(trans-4-Propylcyclohexyl)cyclohexyl]-perfluorooctyl-benzene

4-[trans-4-(trans-4-Butylcyclohexyl)cyclohexyl]-perfluorooctyl-benzene

4-[trans-4-(trans-4-Pentylcyclohexyl)cyclohexyl]-perfluorooctyl-benzene

4-[trans-4-(trans-4-Hexylcyclohexyl)cyclohexyl]-perfluorooctyl-benzene

4-[trans-4-(trans-4-Heptylcyclohexyl)cyclohexyl]-perfluorooctyl-benzene

1-(trans-4-Methylcyclohexyl)-2-(4-perfluorononylphenyl)ethane

1-(trans-4-Ethylcyclohexyl)-2-(4-perfluorononylphenyl)ethane

1-(trans-4-Propylcyclohexyl)-2-(4-perfluorononylphenyl)ethane

1-(trans-4-Butylcyclohexyl)-2-(4-perfluorononylphenyl)ethane

1-(trans-4-Pentylcyclohexyl)-2-(4-perfluorononylphenyl)ethane

1-(trans-4-Hexylcyclohexyl)-2-(4-perfluorononylphenyl)ethane

1-(trans-4-Heptylcyclohexyl)-2-(4-perfluorononylphenyl)ethane

1-(trans-4-Methylcyclohexyl)-2-(4-perfluorooctylphenyl)ethane

1-(trans-4-Ethylcyclohexyl)-2-(4-perfluorooctylphenyl)ethane

1-(trans-4-Propylcyclohexyl)-2-(4-perfluorooctylphenyl)ethane

1-(trans-4-Butylcyclohexyl)-2-(4-perfluorooctylphenyl)ethane

1-(trans-4-Pentylcyclohexyl)-2-(4-perfluorooctylphenyl)ethane

1-(trans-4-Hexylcyclohexyl)-2-(4-perfluorooctylphenyl)ethane

1-(trans-4-Heptylcyclohexyl)-2-(4-perfluorooctylphenyl)ethane

1-[trans-4-(trans-4-Methylcyclohexyl)cyclohexyl]-2-(4-perfluorononylphenyl)-ethane

1-[trans-4-(trans-4-Ethylcyclohexyl)cyclohexyl]-2-(4-perfluorononylphenyl)-ethane

1-[trans-4-(trans-4-Propylcyclohexyl)cyclohexyl]-2-(4-perfluorononylphenyl)-ethane

1-[trans-4-(trans-4-Butylcyclohexyl)cyclohexyl]-2-(4-perfluorononylphenyl)-ethane

1-[trans-4-(trans-4-Pentylcyclohexyl)cyclohexyl]-2-(4-perfluorononylphenyl)-ethane

1-[trans-4-(trans-4-Hexylcyclohexyl)cyclohexyl]-2-(4-perfluorononylphenyl)-ethane

1-[trans-4-(trans-4-Heptylcyclohexyl)cyclohexyl]-2-(4-perfluorononylphenyl)-ethane

1-[trans-4-(trans-4-Methylcyclohexyl)cyclohexyl]-2-(4-perfluorooctylphenyl)-ethane

1-[trans-4-(trans-4-Ethylcyclohexyl)cyclohexyl]-2-(4-perfluorooctylphenyl)-ethane

1-[trans-4-(trans-4-Propylcyclohexyl)cyclohexyl]-2-(4-perfluorooctylphenyl)-ethane

1-[trans-4-(trans-4-Butylcyclohexyl)cyclohexyl]-2-(4-perfluorooctylphenyl)-ethane

1-[trans-4-(trans-4-Pentylcyclohexyl)cyclohexyl]-2-(4-perfluorooctylphenyl)-ethane

1-[trans-4-(trans-4-Hexylcyclohexyl)cyclohexyl]-2-(4-perfluorooctylphenyl)-ethane

1-[trans-4-(trans-4-Heptylcyclohexyl)cyclohexyl]-2-(4-perfluorooctylphenyl)-ethane

1-(trans-4-Methylcyclohexyl)-2-[trans-4-(4-perfluorononylphenyl)-cyclohexyl]-ethane

1-(trans-4-Ethylcyclohexyl)-2-[trans-4-(4-perfluorononylphenyl)-cyclohexyl]-ethane

1-(trans-4-Propylcyclohexyl)-2-[trans-4-(4-perfluorononylphenyl)-cyclohexyl]-ethane

1-(trans-4-Butylcyclohexyl)-2-[trans-4-(4-perfluorononylphenyl)-cyclohexyl]-ethane

1-(trans-4-Pentylcyclohexyl)-2-[trans-4-(4-perfluorononylphenyl)-cyclohexyl]-ethane

1-(trans-4-Hexylcyclohexyl)-2-[trans-4-(4-perfluorononylphenyl)-cyclohexyl]-ethane

1-(trans-4-Heptylcyclohexyl)-2-[trans-4-(4-perfluorononylphenyl)-cyclohexyl]-ethane

1-(trans-4-Methylcyclohexyl)-2-[trans-4-(4-perfluorooctylphenyl)-cyclohexyl]-ethane

1-(trans-4-Ethylcyclohexyl)-2-[trans-4-(4-perfluorooctylphenyl)-cyclohexyl]-ethane

1-(trans-4-Propylcyclohexyl)-2-[trans-4-(4-perfluorooctylphenyl)-cyclohexyl]-ethane

1-(trans-4-Butylcyclohexyl)-2-[trans-4-(4-perfluorooctylphenyl)-cyclohexyl]-ethane

1-(trans-4-Pentylcyclohexyl)-2-[trans-4-(4-perfluorooctylphenyl)-cyclohexyl]-ethane

1-(trans-4-Hexylcyclohexyl)-2-[trans-4-(4-perfluorooctylphenyl)-cyclohexyl]-ethane

1-(trans-4-Heptylcyclohexyl)-2-[trans-4-(4-perfluorooctylphenyl)-cyclohexyl]-ethane

EXAMPLE 13

0.1 mol of dicyclohexylcarbodiimide (DCC) in 30 ml of CH₂ Cl₂ is addedwith stirring at about 10° to a mixture of 0.1 mol of4-(pentafluoroethyl)-phenol (preparation analogously to Bull. Chem. Soc.Japan, 57 (1984) 3361), 0.1 mol oftrans-4-(trans-4-pentylcyclohexyl)cyclohexanecarboxylic acid and 0.01mol of dimethylaminopyridine and 150 ml of CH₂ Cl₂, and the mixture isthen stirred for 15 hours at room temperature. It is filtered oversilica gel, the solvent is evaporated and further purification gives4-(pentafluoroethyl)-phenyltrans-4-(trans-4-pentylcyclohexyl)-cyclohexanoate.

The following are prepared analogously:

4-(Pentafluoroethyl)-phenyltrans-4-(trans-4-methylcyclohexyl)-cyclohexanoate

4-(Pentafluoroethyl)-phenyltrans-4-(trans-4-ethylcyclohexyl)-cyclohexanoate

4-(Pentafluoroethyl)-phenyltrans-4-(trans-4-propylcyclohexyl)-cyclohexanoate

4-(Pentafluoroethyl)-phenyltrans-4-(trans-4-butylcyclohexyl)-cyclohexanoate

4-(Pentafluoroethyl)-phenyltrans-4-(trans-4-hexylcyclohexyl)-cyclohexanoate

4-(Pentafluoroethyl)-phenyltrans-4-(trans-4-heptylcyclohexyl)-cyclohexanoate

EXAMPLE 14

0.1 mol of trans-4-butylcyclohexanecarboxylic acid chloride is added at80° to a mixture of 0.1 mol of 4-(pentafluoroethyl)-phenol (preparationanalogously to Bull. Chem. Soc. Japan, 57, (1984) 3361) and 0.1 mol ofpyridine in 100 ml of toluene, and the mixture is stirred for 3 hours.The pyridine hydrochloride is then filtered off with suction, thetoluene solution is washed with water and dried, and the solvent is thendistilled off. After purification by recrystallization, this gives4-(pentafluoroethyl)-phenyl-trans-4-butylcyclohexanoate.

The following are prepared analogously:

4-(Pentafluoroethyl)-phenyl trans-4-methylcyclohexanoate

4-(Pentafluoroethyl)-phenyl trans-4-ethylcyclohexanoate

4-(Pentafluoroethyl)-phenyl trans-4-propylcyclohexanoate

4-(Pentafluoroethyl)-phenyl trans-4-pentylcyclohexanoate

4-(Pentafluoroethyl)-phenyl trans-4-hexylcyclohexanoate

4-(Pentafluoroethyl)-phenyl trans-4-heptylcyclohexanoate

EXAMPLE 15

With exclusion of moisture, 0.1 mol of DCC in methylene chloride isadded at 5° to a mixture of 0.1 mol oftrans-4-pentylcyclohexanecarboxylic acid, 0.1 mol of hydroquinonemonoperfluoroethyl ether (prepared from 4-perfluoroethyloxybenzoic acidby Hofmann degradation, diazotization and boiling down of the diazoniumsalt), a catalytic quantity of dimethylaminopyridine and methylenechloride. The mixture is then stirred for 12 hours at room temperature,filtered and worked up in the usual way. After purification, this gives4-(pentafluoroethoxy)phenyl trans-4-pentylcyclohexanoate.

The following are prepared analogously:

4-(Pentafluoroethoxy)-phenyl trans-4-methylcyclohexanoate

4-(Pentafluoroethoxy)-phenyl trans-4-ethylcyclohexanoate

4-(Pentafluoroethoxy)-phenyl trans-4-propylcyclohexanoate

4-(Pentafluoroethoxy)-phenyl trans-4-butylcyclohexanoate

4-(Pentafluoroethoxy)-phenyl trans-4-hexylcyclohexanoate

4-(Pentafluoroethoxy)-phenyl trans-4-heptylcyclohexanoate

4-(Pentafluoroethoxy)-phenyltrans-4-(trans-4-methylcyclohexyl)-cyclohexanoate

4-(Pentafluoroethoxy)-phenyltrans-4-(trans-4-(ethylcyclohexyl)-cyclohexanoate

4-(Pentafluoroethoxy)-phenyltrans-4-(trans-4-(propylcyclohexyl)-cyclohexanoate

4-(Pentafluoroethoxy)-phenyltrans-4-(trans-4-(butylcyclohexyl)-cyclohexanoate

4-(Pentafluoroethoxy)-phenyltrans-4-(trans-4-pentylcyclohexyl)-cyclohexanoate

4-(Pentafluoroethoxy)-phenyltrans-4-(trans-4-hexylcyclohexyl)-cyclohexanoate

4-(Pentafluoroethoxy)-phenyltrans-4-(trans-4-heptylcyctohexyl)-cyclohexanoate

EXAMPLE 16

A mixture of 0.1 mol of 4-(trans-4-propylcyclohexyl)-cyclohex-1-ene, 0.1mol of heptafluoropropyl iodide, 10 mol % oftetrakis-(triphenylphosphine)-palladium and 200 ml of hexane is heatedunder reflux for 24 hours (compare T. Ishihara, Chemistry Letters (1986)1895). The isomer mixture of the addition product thus formed is, afterthe catalyst has been filtered off, first heated with tributyl-tinhydride for 90 hours in toluene and reduced. The all-transproduct>.trans-4-(trans-4-propylcyclohexyl)-1-heptafluoropropylcyclohexane,is finally obtained by separating the thiourea inclusion compound from asolution in methanol.

The following are prepared analogously:

trans-4-(trans-4-Butylcyclohexyl)-1-heptafluoropropylcyclohexane

trans-4-(trans-4-Pentylcyclohexyl)-1-heptafluoropropylcyclohexane

trans-4-(trans-4-Heptylcyclohexyl)-1-heptafluoropropylcyclohexane

trans-4-(trans-4-Propylcyclohexyl)-1-nonafluorobutylcyclohexane

trans-4-(trans-4-Butylcyclohexyl)-1-nonafluorobutylcyclohexane

trans-4-(trans-4-Pentylcyclohexyl)-1-nonafluorobutylcyclohexane

trans-4-(trans-4-Heptylbutylcyclohexyl)-1-nonafluorobutylcyclohexane

trans-4-(trans-4-Propylcyclohexyl)-1-tridecafluorohexylcyclohexane

trans-4-(trans-4-Butylcyclohexyl)-1-tridecafluorohexylcyclohexane

trans-4-(trans-4-Pentylcyclohexyl)-1-tridecafluorohexylcyclohexane

trans-4-(trans-4-Heptylcyclohexyl)-1-tridecafluorohexylcyclohexane

1-(trans-4-Propylcyclohexyl)-2-(trans-4-heptafluoropropylcyclohexyl)-ethane

1-(trans-4-Butylcyclohexyl)-2-(trans-4-heptafluoropropylcyclohexyl)-ethane

1-(trans-4-Pentylcyclohexyl)-2-(trans-4-heptafluoropropylcyclohexyl)-ethane

1-(trans-4-Heptylcyclohexyl)-2-(trans-4-heptafluoropropylcyclohexyl)-ethane

1-(trans-4-Propylcyclohexyl)-2-(trans-4-nonafluorobutylcyclohexyl)-ethane

1-(trans-4-Butylcyclohexyl)-2-(trans-4-nonafluorobutylcyclohexyl)-ethane

1-(trans-4-Pentylcyclohexyl)-2-(trans-4-nonafluorobutylcyclohexyl)-ethane

1-(trans-4-Heptylcyclohexyl)-2-(trans-4-nonafluorobutylcyclohexyl)-ethane

1-(trans-4-Propylcyclohexyl)-2-(trans-4-tridecafluorohexylcyclohexyl)-ethan

1-(trans-4-Butylcyclohexyl)-2-(trans-4-tridecafluorohexylcyclohexyl)-ethane

1-(trans-4-Pentylcyclohexyl)-2-(trans-4-tridecafluorohexylcyclohexyl)-ethane

1-(trans-4-Heptylcyclohexyl)-2-(trans-4-tridecafluorohexylcyclohexyl)-ethane

EXAMPLE 17

A mixture of 0.06 mol of1-[trans-4-(trans-4-propylcyclohexyl)-cyclohexyl]-ethene (obtainableanalogously to Negishi, Acc. Chem. Res. 15 (1982) 340 b y coupling ofvinyl bromide withdi-[trans-4-(trans-4-propylcyclohexyl)-cyclohexyl)-zinc), 0.06 mol of4-(3,3,4,4,5,5-heptafluoropentyl)-bromobenzene (preparation analogouslyto R. F. Heck in Org. Reactions, 27 (1982) 345 from 1,4-dibromobenzeneand 3,3,4,4,5,5,5-heptafluoropent-1-ene with subsequent hydrogenation),0.06 mol of triethylamine, 0.27 g of Pd(II) acetate, 0.74 g oftri-o-tolylphosphine and 75 g of acetonitrile is heated for 120 hoursunder reflux.

After evaporation a nd removal of the water-soluble hydrobromide, theproduct is purified by chromatography and hydrogenated in THF over 1.5 gof Pd/C. After working-up and purification, this gives1-[trans-4-(trans-4-propylcyclohexyl)-cyclohexyl]-2-[4-(3,3,4,4,5,5,5-heptafluoropentyl)-phenyl]-ethane.

1-[trans-4-(trans-4-Pentylcyclohexyl)-cyclohexyl]-2-[4-(3,3,4,4,5,5,5-heptafluoropentyl]-ethane

1-[trans-4-(trans-4-Propylcyclohexyl)-cyclohexyl]-2-[4-(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl]-ethane

1-[trans-4-(trans-4-Pentylcyclohexyl)-cyclohexyl]-2-[4-(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl]-ethane

EXAMPLE 18

A mixture of 0.05 mol ofdi-[trans-4-(trans-4-propylcyclohexyl)cyclohexyl]-zinc (preparationanalogously to Luche in J. Org. Chem. 50 (1985) 5761), 0.4 g oftetrakis-(triphenylphosphine)-palladium, 0.05 mol of4-(3,3,4,4,5,5,5-heptafluoropentyl)-bromobenzene (compare Example 17)and THF is stirred for 24 hours at room temperature. After stripping offthe solvent, extracting the residue with dilute HCl/toluene andpurifying the crude product by chromatography and/or recrystallization,this gives4-(3,3,4,4,5,5,5-heptafluoropentyl)-1-[trans-4-(trans-4-propylcyclohexyl)-cyclohexyl]-benzene.

The following are prepared analogously:

4-(3,3,4,4,5,5,5-Heptafluoropentyl)-1-[trans-4-(trans-4pentylcyclohexyl)-cyclohexyl]-benzene

4-(3,3,4,4,5,5,5-Heptafluoropentyl)-1-[trans-4-(trans-4-butylcyclohexyl)-cyclohexyl]-benzene

4-(3,3,4,4,5,5,6,6,7,7,8,8,8-Tridecafluorooctyl)-1-[trans-4-(trans-4-propylcyclohexyl)-cyclohexyl]-benzene

4-(3,3,4,4,5,5,6,6,7,7,8,8,8-Tridecafluorooctyl)-1[trans-4-(trans-4-pentylcyclohexyl)-cyclohexyl]-benzene

4-(3,3,4,4,5,5,6,6,7,7,8,8,8-Tridecafluorooctyl)-1[trans-4-(trans-4-butylcyclohexyl)-cyclohexyl]-benzene

EXAMPLE 19

0.05 mol of trans-4-propylcyclohexanecarboxylic acid chloride in 10 mlof toluene is added in (sic) a mixture of 0.05 mol of pyridine and4-(3,3,4,4,5,5,5-heptafluoropentyl)-phenol (obtainable via a Heckcoupling of 4-bromophenyl benzyl ether with3,3,4,4,5,5,5-heptafluoropent-1-ene and subsequent hydrogenation andether cleavage) and the mixture is stirred for 24 hours at roomtemperature. Hours (sic). After working-up and purification, this gives4-(3,3,4,4,5,5,5-heptafluoropentyl)phenyl trans-4-propylcyclohexanoate.

The following are prepared analogously:

4-(3,3,4,4,5,5,5-Heptafluoropentyl)-phenyl trans-4-butylcyclohexanoate

4-(3,3,4,4,5,5,5-Heptafluoropentyl)-phenyl trans-4-pentylcyclohexanoate

4-(3,3,4,4,5,5,5-Heptafluoropentyl)-phenyl trans-4-heptylcyclohexanoate

4-(3,3,4,4,5,5,6,6,6-Nonafluorohexyl)-phenyltrans-4-propylcyclohexanoate

4-(3,3,4,4,5,5,6,6,6-Nonafluorohexyl)-phenyl trans-4-butylcyclohexanoate

4-(3,3,4,4,5,5,6,6,6-Nonafluorohexyl)-phenyltrans-4-pentylcyclohexanoate

4-(3,3,4,4,5,5,6,6,6-Nonafluorohexyl)-phenyltrans-4-heptylcyclohexanoate

4-(3,3,4,4,5,5,6,6,7,7,8,8,8-Tridecafluorooctyl)-phenyltrans-4-propyl-cyclohexanoate

4-(3,3,4,4,5,5,6,6,7,7,8,8,8-Tridecafluorooctyl)-phenyltrans-4-butyl-cyclohexanoate

4-(3,3,4,4,5,5,6,6,7,7,8,8,8-Tridecafluorooctyl)-phenyltrans-4-pentyl-cyclohexanoate

4-(3,3,4,4,5,5,6,6,7,7,8,8,8-Tridecafluorooctyl)-phenyltrans-4-heptyl-cyclohexanoate

4-(3,3,4,4,5,5,5-Heptafluoropentyl)-phenyltrans-4-(trans-4-propylcyclohexyl)-cyclohexanoate

4-(3,3,4,4,5,5,5-Heptafluoropentyl)-phenyltrans-4-(trans-4-butylcyclohexyl)-cyclohexanoate

4-(3,3,4,4,5,5,5-Heptafluoropentyl)-phenyltrans-4-(trans-4-pentylcyclohexyl)-cyclohexanoate

4-(3,3,4,4,5,5,5-Heptafluoropentyl)-phenyltrans-4-(trans-4-heptylcyclohexyl)-cyclohexanoate

4-(3,3,4,4,5,5,6,6,6-Nonafluorohexyl)-phenyltrans-4-(trans-4-propylcyclohexyl)-cyclohexanoate

4-(3,3,4,4,5,5,6,6,6-Nonafluorohexyl)-phenyltrans-4-(trans-4-butylcyclohexyl)-cyclohexanoate

4-(3,3,4,4,5,5,6,6,6-Nonafluorohexyl)-phenyltrans-4-(trans-4-pentylcyclohexyl)-cyclohexanoate

4-(3,3,4,4,5,5,6,6,6-Nonafluorohexyl)-phenyltrans-4-(trans-4-heptylcyclohexyl)-cyclohexanoate

4-(3,3,4,4,5,5,6,6,7,7,8,8,8-Tridecafluorooctyl)phenyltrans-4-(trans-4-propylcyclohexyl)-cyclohexanoate

4-(3,3,4,4,5,5,6,6,7,7,8,8,8-Tridecafluorooctyl)phenyltrans-4-(trans-4-butylcyclohexyl)-cyclohexanoate

4-(3,3,4,4,5,5,6,6,7,7,8,8,8-Tridecafluorooctyl)phenyltrans-4-(trans-4-pentylcyclohexyl)-cyclohexanoate

4-(3,3,4,4,5,5,6,6,7,7,8,8,8-Tridecafluorooctyl)phenyltrans-4-(trans-4-heptylcyclohexyl)-cyclohexanoate

EXAMPLE 20

A mixture of 0.05 mol of1-[trans-4-(trans-4-propylcyclohexyl)-cyclohexyl]-ethene (compareExample 17 for preparation), 0.05 mol of heptafluoropropyl iodide, 10mol % of tetrakis-(triphenylphosphine)-palladium and 100 ml of hexane isreacted analogously to Example 16. The addition product is isolated bymeans of purification by chromatography and reduced analogously), toExample 16. After purification by chromatography using hexane oversilica gel, this givestrans-4-(trans-4-propylcyclohexyl)-1-(3,3,4,4,5,5,5-heptafluoropentyl)-cyclohexane.

The following are prepared analogously:

trans-4-(trans-4-Butylcyclohexyl)-1-(3,3,4,4,5,5,5-heptafluoropentyl)-cyclohexane

trans-4-(trans-4-Pentylcyclohexyl)-1-(3,3,4,4,5,5,5-heptafluoropentyl)-cyclohexane

trans-4-(trans-4-Heptylcyclohexyl)-1-(3,3,4,4,5,5,5-heptafluoropentyl)-cyclohexane

trans-4-(trans-4-(Propylcyclohexyl)-1-(3,3,4,4,5,5,6,6,6-nonafluorohexyl)-cyclohexane

trans-4-(trans-4-Butylcyclohexyl)-1-(3,3,4,4,5,5,6,6,6-nonafluorohexyl)-cyclohexane

trans-4-(trans-4-Pentylcyclohexyl)-1-(3,3,4,4,5,5,6,6,6-nonafluorohexyl)-cyclohexane

trans-4-(trans-4-Heptylcyclohexyl)-1-(3,3,4,4,5,5,6,6,6-nonafluorohexyl)-cyclohexane

trans-4-(trans-4-Propylcyclohexyl)-1-(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl)-cyclohexane

trans-4-(trans-4-Butylcyclohexyl)-1-(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl)-cyclohexane

trans-4-(trans-4-Pentylcyclohexyl)-1-(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl)-cyclohexane

trans-4-(trans-4-Heptylcyclohexyl)-1-(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl)-cyclohexane

EXAMPLE 21

The mixture of 0.03 mol of p-(5-heptyl-pyrimidin-2-yl)-bromobenzene,0.036..(sic) of 2,2,3,3-tetrafluoropropyl acrylate, 0.03 mol oftriethylamine, 0.14 g of Pd(II) acetate, 0.4 g of tri-o-tolylphosphineand 75 ml of acetonitrile is heated under reflux for 36 hours. Themixture is then cooled to 0°, and the crude product is filtered off andwashed with acetonitrile and water. After purification bycrystallization, this gives 2,2,3,3-tetrafluoropropylp-(5-heptyl-pyrimidin-2-yl)-cinnamate of m.p. 35° and c.p. 108°.

The following are prepared analogously:

2,2,3,3-Tetrafluoropropyl p-(5-ethyl-pyrimidin-2-yl)cinnamate

2,2,3,3-Tetrafluoropropyl p-(5-propyl-pyrimidin-2-yl)cinnamate

2,2,3,3-Tetrafluoropropyl p-(5-butyl-pyrimidin-2-yl)cinnamate

2,2,3,3-Tetrafluoropropyl p-(5-pentyl-pyrimidin-2-yl)cinnamate

2,2,3,3-Tetrafluoropropyl p-(5-hexyl-pyrimidin-2-yl)cinnamate

1H,1H,5H-Octafluoropentyl p-(5-heptyl-pyrimidin-2-yl)cinnamate, m.p.84°, c.p. 117°

1H,1H,5H-Octafluoropentyl p-(5-ethyl-pyrimidin-2-yl)cinnamate

1H,1H,5H-Octafluoropentyl p-(5-propyl-pyrimidin-2-yl)cinnamate

1H,1H,5H-Octafluoropentyl p-(5-butyl-pyrimidin-2-yl)cinnamate

1H,1H,5H-Octafluoropentyl p-(5-pentyl-pyrimidin-2-yl)cinnamate

1H,1H,5H-Octafluoropentyl p-(5-hexyl-pyrimidin-2-yl)cinnamate

1H,1H,2H,2H-Heptadecafluorodecyl p-(5-heptyl-pyrimidin-2-yl)-cinnamate

1H,1H,2H,2H-Heptadecafluorodecyl p-(5-ethyl-pyrimidin-2-yl)-cinnamate

1H,1H,2H,2H-Heptadecafluorodecyl p-(5-propyl-pyrimidin2-yl)-cinnamate

1H,1H,2H,2H-Heptadecafluorodecyl p-(5-butyl-pyrimidin-2-yl)-cinnamate

1H,1H,2H,2H-Heptadecafluorodecyl p-(5-pentyl-pyrimidin-2-yl)-cinnamate

1H,1H,2H,2H-Heptadecafluorodecyl p-(5-hexyl-pyrimidin-2-yl)-cinnamate

EXAMPLE 22

0.01 mol of 2,2,3,3-tetrafluoropropylp-(5-heptyl-pyrimidin-2-yl)-cinnamate (for preparation see Example 21)are hydrogenated in THF with Pd/C in the known manner. Usual working-upgives 2,2,3,3-tetrafluoropropylβ-[p-(5-heptyl-pyrimidin-2-yl)-phenyl]-propionate of m.p. 42° and c.p.54°.

The following are prepared analogously:

2,2,3,3-Tetrafluoropropylβ-[p-(5-ethyl-pyrimidin-2-yl)phenyl]-propionate

2,2,3,3-Tetrafluoropropylβ-[p-(5-propyl-pyrimidin-2-yl)phenyl]-propionate

2,2,3,3-Tetrafluoropropylβ-[p-(5-butyl-pyrimidin-2-yl)phenyl]-propionate

2,2,3,3-Tetrafluoropropylβ-[p-(5-pentyl-pyrimidin-2-yl)phenyl]-propionate

2,2,3,3-Tetrafluoropropylβ-[p-(5-hexyl-pyrimidin-2-yl)phenyl]-propionate

1H,1H,5H-Octafluoropentyl β-[p-(heptyl-pyrimidin-2-yl)phenyl]-propionate

1H,1H,5H-Octafluoropentyl β-(p-(ethyl-pyrimidin-2-yl)phenyl]-propionate

1H,1H,5H-Octafluoropentyl β-(p-(propyl-pyrimidin-2-yl)phenyl]-propionate

1H,1H,5H-Octafluoropentyl β-(p-(butyl-pyrimidin-2-yl)phenyl]-propionate

1H,1H,5H-Octafluoropentyl β-(p-pentyl-pyrimidin-2-yl)phenyl]-propionate

1H,1H,5H-Octafluoropentyl β-(p-hexyl-pyrimidin-2-yl)phenyl]-propionate

1H,1H,2H,2H-Heptadecafluorodecylβ-[p-(5-heptyl-pyrimidin-2-yl)-phenyl]-propionate

1H,1H,2H,2H-Heptadecafluorodecylβ-[p-(5-ethyl-pyrimidin-2-yl)-phenyl]-propionate

1H,1H,2H,2H-Heptadecafluorodecylβ-[p-(5-propyl-pyrimidin-2-yl)-phenyl]-propionate

1H,1H,2H,2H-Heptadecafluorodecylβ-[p-(5-butyl-pyrimidin-2-yl)-phenyl]-propionate

1H,1H,2H,2H-Heptadecafluorodecylβ-[p-(5-pentyl-pyrimidin-2-yl)-phenyl]-propionate

1H,1H,2H,2H-Heptadecafluorodecylβ-[p-(5-hexyl-pyrimidin-2-yl)-phenyl]-propionate

EXAMPLE 23

A mixture of 0.2 mol oftrans-4-(trans-4-propyl-cyclohexyl)-cyclohexylmethyl iodide, 0.2 mol oftriphenylphosphine and 250 ml of acetonitrile is heated under reflux for18 hours. After evaporation of the solvent and crystallization of theresidue from toluene, 250 ml of THF and 0.2 mol oftetrafluoroethoxybenzaldehyde are added to the salt. A solution of 0.2mol of potassium tert.-butylate in 150 ml of THF is added thereto at0°-5° and the mixture is stirred for 1 hour at room temperature. It isthen neutralized with dilute HCl, filtered and evaporated, and theresidue is purified by crystallization. The olefin thus obtained ishydrogenated in THF over Pd/C (5%) at room temperature and under normalpressure.

Working-up in the usual way and purification by crystallization gives1-[trans-4-(trans-4-propylcyclohexyl)-cyclohexyl]-2-(4-tetrafluoroethoxyphenyl)-ethane.

The following are prepared analogously:

1-[trans-4-(trans-4-Butylcyclohexyl)cyclohexyl]-2-(4-tetrafluoroethoxyphenyl)-ethane

1-[trans-4-(trans-4-Ethylcyclohexyl)cyclohexyl]-2-(4-tetrafluoroethoxyphenyl)-ethane

1-[trans-4-(trans-4-Pentylcyclohexyl)cyclohexyl]-2(4-tetrafluoroethoxyphenyl)-ethane

1-[trans-4-(trans-4-Hexylcyclohexyl)cyclohexyl]-2(4-tetrafluoroethoxyphenyl)-ethane

1-[trans-4-(trans-4-heptylcyclohexyl)cyclohexyl]-2(4-tetrafluoroethoxyphenyl)-ethane

1-(trans-4-Propylcyclohexyl)-2-(4-tetrafluoroethoxyphenyl)-ethane

1-(trans-4-Butylcyclohexyl)-2-(4-tetrafluoroethoxyphenyl)-ethane

1-(trans-4-Ethylcyclohexyl)-2-(4-tetrafluoroethoxyphenyl)-ethane

1-(trans-4-Pentylcyclohexyl)-2-(4-tetrafluoroethoxyphenyl)-ethane

1-(trans-4-Hexylcyclohexyl)-2-(4-tetrafluoroethoxyphenyl)-ethane

1-(trans-4-Heptylcyclohexyl)-2-(4-tetrafluoroethoxyphenyl)-ethane

EXAMPLE 24

A mixture of 0.2 mol of4-[trans-4-(trans-4-propylcyclohexyl)-cyclohexyl]-phenol (obtainablefrom the corresponding ethyl ether by ether cleavage), 80 ml of dioxaneand 0.05 mol of sodium is stirred for 2.5 hours at room temperature. 40ml of DMF are then added and the phenolate solution is heated in anautoclave with tetrafluoroethylene (2.7 bar) to 50°-70° with stirring.

This procedure is repeated until the pressure remains constant.

The reaction mixture is then treated with water and worked-up in theusual way. After purification by crystallization, this gives4-[trans-4-(trans-4-propylcyclohexyl)-cyclohexyl]-tetrafluoroethoxybenzene.

The following are prepared analogously:

4-[trans-4-(trans-4-Ethylcyclohexyl)cyclohexyl]tetrafluoroethoxybenzene

4-[trans-4-(trans-4-Butylcyclohexyl)cyclohexyl]tetrafluoroethoxybenzene

4-[trans-4-(trans-4-Pentylcyclohexyl)cyclohexyl]tetrafluoroethoxybenzene

4-[trans-4-(trans-4-Hexylcyclohexyl)cyclohexyl]tetrafluoroethoxybenzene

4-[trans-4-(trans-4-Heptylcyclohexyl)cyclohexyl]tetrafluoroethoxybenzene

EXAMPLE 25

A mixture of 0.1 mol of 4-tetrafluoroethoxybenzaldehyde, 0.12 mol ofm-chloroperbenzoic acid and 250 ml of CH₂ Cl₂ is stirred for 48 hours atroom temperature. The reaction mixture is washed with H₂ O, dried andevaporated. The residue stirred for 2.5 hours at room temperature with200 ml of about 8% NaOH. The mixture is then washed with petroleum etherand acidified. The phenol is taken up in CH₂ Cl₂, and the phase iswashed with water, dried and evaporated.

0.1 mol of pyridine is added, while cooling with ice, to this crudeproduct with 0.1 mol of trans-4-pentylcyclohexylcarboxylic acid chloridein 100 ml of CH₂ Cl₂. Stirring is continued for 6 hours at roomtemperature, and the mixture is worked-up by extraction. Afterpurification by crystallization this gives 4-tetrafluoroethoxyphenyltrans-4-pentylcyclohexanecarboxylate.

The following are prepared analogously:

4-Tetrafluoroethoxyphenyl trans-4-ethylcyclohexanecarboxylate

4-Tetrafluoroethoxyphenyl trans-4-butylcyclohexanecarboxylate

4-Tetrafluoroethoxyphenyl trans-4-propylcyclohexanecarboxylate

4-Tetrafluoroethoxyphenyl trans-4-hexylcyclohexanecarboxylate

4-Tetrafluoroethoxyphenyl trans-4-heptylcyclohexanecarboxylate

4-Tetrafluoroethoxyphenyltrans-4-(trans-4-pentylcyclohexyl)-cyclohexanecarboxylate

4-Tetrafluoroethoxyphenyltrans-4-(trans-4-ethylcyclohexyl)-cyclohexanecarboxylate

4-Tetrafluoroethoxyphenyltrans-4-(trans-4-butylcyclohexyl)-cyclohexanecarboxylate

4-Tetrafluoroethoxyphenyltrans-4-(trans-4-propylcyclohexyl)-cyclohexanecarboxylate

4-Tetrafluoroethoxyphenyltrans-4-(trans-4-hexylcyclohexyl)-cyclohexanecarboxylate

4-Tetrafluoroethoxyphenyltrans-4-(trans-4-heptylcyclohexyl)-cyclohexanecarboxylate

EXAMPLE 26

0.05 mol of n-butyllithium is added at -10°-0° to a mixture of 0.05 molof 4-bromo-tetrafluoroethoxybenzene and 200 ml of ether. 0.05 mol of4-(trans-4-pentyl-cyclohexylethyl)-cyclohexanone (obtainable by reactingmethoxybenzene with trans-4-pentylcyclohexylmethylcarboxylic acidchloride in the presence of AlCl₃, subsequent hydrogenation with H₂ /Pd,reaction with HBr and repeated hydrogenation with H₂ /Raney nickel) in50 ml of ether is then added at this temperature. The mixture is stirredfor 1 hour at room temperature and worked up by extraction, and theresulting residue is boiled for 2 hours with 1 g of p-toluenesulfonicacid and 200 ml of toluene under a water separator.

The cyclohexene compound thus obtained is hydrogenated pressure in THFover 1 g of Pd/C under normal pressure. The mixture is worked up and,after purification by crystallization, this gives1-(trans-4-pentylcyclohexyl)2-[trans-4-(4-tetrafluoroethoxyphenyl)-cyclohexyl]-ethane.

The following are prepared analogously:

1-(trans-4-Ethylcyclohexyl)-2-[trans-4-(4-tetrafluoroethoxyphenyl)-cyclohexyl]-ethane

1-(trans-4-Propylcyclohexyl)-2-[trans-4-(4-tetrafluoroethoxyphenyl)-cyclohexyl]-ethane

1-(trans-3-Butylcyclohexyl)-2-[trans-4-(4-tetrafluoroethoxyphenyl)-cyclohexyl]-ethane

1-(trans-4-Hexylcyclohexyl)-2-[trans-4-(4-tetrafluoroethoxyphenyl)-cyclohexyl]-ethane

1-(trans-4-Heptylcyclohexyl)-2-[trans-4-(4-tetrafluoroethoxyphenyl)-cyclohexyl]-ethane

We claim:
 1. An electrooptical liquid crystal display element,containing a dielectric with at least two liquid crystalline components,which dielectric comprises at least one fluorine-containing compound ofthe formula I

    R.sup.1 --(A.sup.1 --Z.sup.1).sub.m --A.sup.2 --R.sup.2    I

wherein R¹ is H, F, Cl, Br, --CN, --NCS or an unsubstitutedstraight-chain alkyl group having 1-15 C atoms, in which one or two CH₂groups are optionally replaced by --O--, --CO--, --O--CO--, --CO--O--,--C.tbd.C--, or --CH═CH--, no 2 heteroatoms being linked to one another;R² is perfluoroalkoxy of not more than 15 carbon atoms, and having atleast 2 CF2 groups in which one or more CF₂ groups are optionallyreplaced by --CF═CF--, A¹ is 1,4-phenylene which is unsubstituted orsubstituted by one or two F or Cl atoms or CH₃ groups or CN groups, andin which one or two CH Groups are optionally replaced by N atoms;1,4-cyclohexylene in which one or two non-adjacent CH₂ groups areoptionally replaced by O atoms or S atoms; piperidine-1,4-diyl;1,4-bicyclo[2.2.2]octylene, unsubstituted or CN-- substituteddecahydronaphthaline-2,6-diyl or 1,2,3,4-tetrahydronaphthaline-2,6-diyl;A² is 1,4-phenylene which is substituted by one or two F atoms; m is 1,2, or 3; and Z¹ is --CO--O--, --O--CO--, --OCH₂ --, --CH₂ O--, --CH₂ CH₂-- or a single bond,it being possible for multiple groups A¹ to beidentical or different and for multiple groups Z¹ to be identical ordifferent in the case where M=2 or 3, whereby said element is based onthe twisted cell, guest-host, deformation of aligned phase, dynamicscattering, SBE or STN effects.
 2. An electrooptical liquid crystaldisplay element according to claim 1, whereinR² is perfluoroalkoxy of2-15 carbon atoms; A¹ is 1,4-phenylene which is unsubstituted orsubstituted by one or two F atoms, and in which one or two CH groups areoptionally replaced by N atoms, 1,4-cyclohexylene in which one or twonon-adjacent CH₂ groups are optionally replaced by O atoms; Z¹ is --CH₂CH₂ -- or a single bond,it being possible for multiple groups A¹ to beidentical or different and for multiple groups Z¹ to be identical ordifferent in the case where M=2 or
 3. 3. An electrooptical liquidcrystal display element according to claim 1 whereinR² is --OC₂ F₅. 4.An electrooptical liquid crystal display element according to claim 2,whereinR² is --OC₂ F₅.
 5. AN electrooptical liquid crystal displayelement, containing a dielectric with at least two liquid crystallinecomponents, wherein the dielectric comprises at least onefluorine-containing compounds whichis:p-[trans-4-(trans-4-methylcyclohexyl)cyclohexyl]pentafluoroethoxybenzene,p-[trans-4-(trans-4-ethylcyclohexyl)cyclohexyl]pentafluoroethoxybenzene,p-[trans-4-(trans-4-propylcyclohexyl)cyclohexyl]pentafluoroethoxybenzene,p-[trans-4-(trans-4-butylcyclohexyl)cyclohexyl]pentafluoroethoxybenzene,p-[trans-4-(trans-4-pentylcyclohexyl)cyclohexyl]pentafluoroethoxybenzene,p-[trans-4-(trans-4-hexylcyclohexyl)cyclohexyl]pentafluoroethoxybenzene,orp-[trans-4-(trans-4-heptylcyclohexyl)cyclohexyl]pentafluoroethoxybenzene,andwherein said element is based on the twisted cell, guest-host,deformation of aligned phase, dynamic, scattering SBE or STN effect.